Author: Rick

A DM for *mumble* years, I've been playing AD&D since junior high. I've currently got two separate campaigns running, both in Mystara. I've been told when they handed out hobbies, I stood in the short lines. I actively cycle tour, kayak, play board games, read, develop home automation software, play Stars!, volunteer with the International and National American Red Cross, and work on a never-ending stream of home repairs. In my wake I've left paintball, medieval full-contact combat (SCA), computer gaming, Heroclix, and kite construction.

ARRGGHHH I’m Psionic

Last Updated: 231214…250906
psionics@corwyn.net

This article extends my “Oops” series, but psionics are far more of a mess than usual. In the roughly 8 pages discussing psionics between the PHB and DMG , the words that quantify psionics  include: psionic ability, psionic strength total, total psionic ability, psionic ability, total psionic strength, psionic strength, psionic attack strength, psionic defense strength, psionic attack points, and psionic defense points. To exacerbate things, psionics operate by segment, yet AD&D initiative really, well, doesn’t.  Herein lies my attempt to adjust the vocabulary and rules to be understandable but functionally equivalent, filling in the usual gaps. Much like hit points, references to a value or strength are the current value or strength, not the original.

Determining Psionics

Only humans (potentially dwarves, halflings, and rarely elves) can be psionic. Starting characters with an intelligence, wisdom, or charisma of at least 16 roll d100. For each point of intelligence above 16 add 2.5 to the roll, for each point of wisdom above 16 add 1.5 to the roll, and for each point of charisma above 16 add .5 to the roll. Drop any fraction. Any result of 100+ indicates the character has psionic ability.

If so, roll a base d100. Next, determine bonus points: 1 point for each point of intelligence, wisdom and charisma above 12. If 2 of these scores are above 16, the bonus points are doubled. If all 3 scores are above 16, the bonus points are quadrupled. The base (01-100) plus bonus points (4-72), are added together. That number equates to the attack strength, and also the defense strength. Psionic strength always equals (attack strength + defense strength)—a number therefore from 10 to 344.  Psionic strength is used for psionic combat, and in the employment of disciplines.

Should a non-psionic character have their intelligence, wisdom or charisma permanently increase, check again to determine if they have psionic ability. Should intelligence, wisdom or charisma permanently change for a psionic character, adjust the attack and defense strength (and thus psionic strength).  If an ability change leaves the character without at least one necessary 16, they lose their psionic ability (temporarily or permanently, depending). A wish can grant (or remove!) psionics as long as the recipient has a necessary 16 in intelligence, wisdom, or charisma.

Attack Modes

A psionic character can have up to five attack modes. How many are determined by another d100 roll:

01-25 1 attack mode
26-50 2 attack modes
51-75 3 attack modes
76-95 4 attack modes
96-00 5 attack modes

The player then chooses from the five available attack modes:

Attack Mode Attack Strength Cost  per Segment Attack Range4
Short Medium Long
A. Psionic Blast1 20 2″ 4″ 6″
B. Mind Thrust 4 3″ 6″ 9″
C. Ego Whip 7 4″ 8″ 12″
D. Id Insinuation2 10 6″ 12″ 18″
E . Psychic Crush3 14 5″ – –

 1A cone-shaped wave of force 1/2″ diameter at its source and 2″ diameter at its terminus (6″ distance).

2Id Insinuation affects all psionically-aware creatures in a 2″ X 2″ area within the attack range.

3If Psychic Crush is used the attacker may only defend with mode G (Thought Shield), or have no defense at all. Those killed by Psychic Crush lose all psionic abilities if raised or resurrected.

4Expending double or treble the attack strength will double or treble the range of modes B, C, and D.

Defense Modes

A character will also have up to five defense modes. How many are determined by another d100 roll:

01-25 2 defense modes
26-75 3 defense modes
76-90 4 defense modes
91-00 5 defense modes

The player then chooses from the five available defense modes; the first choice must be Mind Blank:

Defense Mode Defense Strength Cost per Segment Area of Effect1
F. Mind Blank 1 Individual only
G. Thought Shield4 2 Individual only
H. Mental Barrier 3 Individual only
I. Intellect Fortress 8 10’r. of individual2
J. Tower of Iron Will 10 3’r. of individual3

1If the defense mode has an area of effect (AoE) beyond the individual, it offers either its defense or the defense used by any individual within its radius, whichever is better.
2Intellect Fortress offers non-psionics in the AoE +2 on saving throws versus Psionic Blast.
3Tower of Iron Will offers non-psionics in the AoE +6 on saving throws versus Psionic Blast.
4If Thought Shield is the only defense mode used in the round, the creature can maintain it while using a discipline, fighting, casting a spell, or being involved in some other activity for the round that does not include any psionic attacks, still at a cost of 2 per segment. Thought Shield is also the only defense that can be used in conjunction with attacking via Psychic Crush.

Psionic Disciplines

A psionic character determines how many disciplines they will have with a d100 roll:

Die Score Number of Minor Disciplines Number of Major Disciplines
01-10 1 0
11-25 2 0
26-40 3 0
41-55 2 1
56-70 3 1
71-80 4 1
81-90 3 2
91-95 5 1
96-100 4 2

After determining the number of disciplines, roll on the Table of Psionic Disciplines (see PHB) for which disciplines are known. If the same discipline is rolled more than once or excluded for the character’s class, re-roll. Select one minor discipline to be begin at first level, with one additional discipline (all minor disciplines first) usable for each 2 additional levels of experience in the character’s class.  The level of mastery is how many character levels the character has had access to the discipline (e.g., a 3rd level character who just gained access to Empathy would use it at 1st level of mastery; at 4th (character) level they would use the discipline at 2nd level of mastery).

The psionic strength cost for disciplines applies to both attack and defense strengths. 1 psionic strength equals 1 attack strength and 1 defense strength.

It is never possible to use two disciplines at the same time, or use an attack mode and a discipline at the same time.

Combined Psionic Operations

Psionic creatures can operate together to increase the range of shared disciplines where range is a factor and otherwise possible. Multiple psionic creatures can link their minds to add a cumulative 50% to the range of a discipline (100% + [n] × 50%, e.g., two individuals have 200% of the range; 3 individuals have 250%, etc.). The base range is always that of the individual in the group with the shortest range.

It is also possible for two or more creatures to increase their psionic strength for psionic combat. Such an operation must be in “series”, with the creatures adding 20% of their current psionic strength (half attack strength, half defense strength, all fractions rounded up) to the next individual in the series. Example: Creature A has a psionic strength of 100, so 20 psionic strength (10 attack strength, 10 defense strength) are transferred to creature B to bring its total from 120 to 140, and B then transfers 28 psionic strength (again, 20%) to creature C whose psionic strength is 130 but is now 158s, and then C transfers 158 × .20, or 32 psionic strength to final creature D. All series begin from the creature with the lowest psionic strength. The final creature in the series attacks and defends for all in the series. Only the final creature in the series can psionically attack or be attacked. All psionic strength used first comes from the transferred psionic strength. All creatures in the series will be affected by all psionic attacks affecting the final creature.

The series is maintained even for distracted creatures; they are unable to attack or defend (psionically or otherwise) until the series is dissolved by the lead creature in the series. Dissolving the series also removes the transferred psionic strength. The death or distraction of a creature earlier in the series will not disrupt the series.

Recovery

Psionic strength can be restored by refraining from psionic activity. Disciplines which do not require continuing strength point outlay can be in operation during recovery periods. No psionic strength can be recovered in less than one-hour increments.   The rate of restoration depends upon the activity level:

Physical Activity1, 2 Psionic Strength Recovered (half attack, half defense)
hard exertion none
walking and like activity 3 psionic strength  / hour
sitting and talking or reading 6 psionic strength / hour
resting and meditating 12 psionic strength / hour
sleeping 12 psionic strength / hour

1The least favorable activity is considered for each hour of time spent in restoration of psionic strength.
2Psionic strength can be recovered on the Astral plane at the rate of 6 psionic strength / hour when moving by mental effort, and 12 psionic strength/hour when “floating” and not thinking of moving.

Psionic Combat

Psionic combat is a declared action for a round, but starting on the first segment of the round regardless of initiative (potentially superseding the declared action of others now abruptly psionic combatants). Psionic combat can occur during Surprise if the initiator’s party is unsurprised. In that case, psionic combat will occur on each segment of surprise—both sides interact psionically as normal (both attack and defense) for each segment of Surprise.

Each psionic attack or defense will cost attack or defense strength (respectively), depending on the selected attack mode, defense mode, and resulting outcome. Creatures using a defense mode can take another action (using an attack mode, discipline, OR a segment of movement). Creatures using an attack mode cannot engage in any other activity but using a defense mode. If a creature is distracted by physical attack or spell damage or effect (such as charm, hold, etc.) it cannot make further psionic attacks or take other actions that round (but could resume the next round), although a distracted creature can still utilize defense modes.

There is one exception—Thought Shield. A psionic combatant who selects Thought Shield in the first segment of psionic combat can maintain this defense mode (spending defense strength each segment) while pursuing another non-psionic action for the round (or during surprise). However, taking a non-psionic action precludes making any psionic attacks for the entirety of the round.

Psionic vs. Psionic

All psionic attacks and defenses are simultaneous. Psionic combat (presuming Creatures A & B) takes place by segment, starting on the first segment of the round:

  1. Determine A & B’s current psionic strength (attack strength + defense strength).
  2. A & B announce their own attack mode (from those they have available).
    1. If all attack strength is expended, or not enough attack strength remains to use any attack mode available, the creature may defend only.
  3. A & B only then choose their own defense mode (using the most applicable from those available).
  4. Compare each creature’s attack mode and psionic strength to their opponent’s chosen defense on the appropriate Psionic vs. Psionic table, Appendix A(Short Range), or Appendix B (Medium/Long Range).
    1. Long range attacks reduce the attacker’s effective psionic strength by 25 for purposes of the table
  5. Psionic attacks at short range reduce each creature’s defense strength by the defense cost (see Appendix A). Psionic attacks at medium and long range reduce that damage by 20% (see Appendix B). If the attack was long range, and originally in the 1-25 point range for psionic strength, damage is reduced by 50% instead of 20%. Any results beyond that required to bring the defense strength to 0 is applied to hit points.
  6. Reduce each creature’s attack strength by the cost of their attack, taking into account any increased cost for increasing the range.
  7. Repeat this sequence each segment for 10 segments, or until neither side makes a psionic attack during a segment.

Defenseless Psionics

Once a psionic creature’s defense strength reaches 0 (or has no available defense mode), later psionic attacks are determined on the Psionic Vs. Defenseless Psionic table (see Appendix C):

  • Determine the attacker’s attack strength and attack mode.
  • Determine the defender’s psionic strength (typically equal to their attack strength, as defense strength likely equals 0).
  • Compare the attacker’s attack strength and attack mode to the defender’s psionic strength (e.g., their attack strength) on the Psionic Vs. Defenseless Psionic table (see Appendix C).
    • A number result on the table reduces the defender’s psionic strength, defense strength first. If the attack strength reaches 0, reduce the defender’s hit points by the remainder of the number.
    • If the result is a letter, apply that result to the defender.
      For a defender with mind bar, letter results only apply when the psionic strength is 0 at the beginning of the segment, otherwise they lose 40 psionic strength (half attack strength, half defense strength first, and then any remaining psionic strength), applying any leftover results to hit points.

Psionic Blast on non-Psionics

Only psionic blast can affect non-psionic creatures, and only if the psionically-attacking creature has an attack strength of 100+.   Each non-psionic potentially affected by psionic blast rolls a “saving throw” (See Appendix D) based on their total intelligence and wisdom to avoid the effect, adjusted by various factors:

 

Attacked Creature’s
Int + Wisdom		 Saving Throw
0-5 20
6-9 18
10-13 16
14-17 14
18-21 12
22-25 10
26-29 8
30-33 6
34-35 4
36-37 2
38 & up 0

 

Saving Throw Adjustments
Bonuses   Penalties
medium range +1   panicked -1
long range +2   enraged -1
magic-user +1   confused -2
cleric +2   hopeless -3
elf +2   stunned -3
Intellect Fortress within 10′ +2   using psionic-related power2 -4
mink blank spell +2   using ESP -5
dwarf +4   feebleminded3 –
halfling +4   insane4 –
helm of telepathy1 +4      
Tower of Iron Will within 3′ +6      
mind bar +6      
protection items valid against “all forms of attack”5 +x      

1The helm of telepathy will cause the attacker to be stunned for 1-4 rounds if the defender’s saving throw is successful.

2These powers or spells are: astral protection/spell, augury, charm monster, charm person, clairaudience, clairvoyance, confusion, detect evil/good, detect magic, dimension door, divination, empathy, enlarge, ESP, etherealness, feeblemind, feign death, geas, invisibility (any sort), know alignment, levitation, locate object, magic jar, plane shift, polymorph self, quest, shape change, suggestion, symbol, telekinesis, telepathy, teleportation, true seeing

3A feebleminded person has a combined intelligence and wisdom score of 0-5.

4Insane creatures cannot be psionically attacked.

5rings and cloaks of protection

In the Psionic Blast on Non-Psionics table (Appendix D), the attacked creature’s total intelligence and wisdom is used to figure saving throws. However, wisdom is not a standard given attribute of monsters. To compute the wisdom of non-psionic monsters, use the following table:

Intelligence of Creature Wisdom Range
Below Low 0
Low 2d4
Average 3d4
Very/Highly 4d4
Exceptional/Genius 2d6+6
Supra-Genius 4d4+4
Godlike 3d6+6

Random Encounters

If a random encounter occurs when the party has used psionic powers during the last turn (or spells resembling disciplines during the last round), there is a 1 in 4 chance the encounter is psionic. If so, use the Psionic Encounter Table instead. The psionic encounter otherwise occurs as normal, although certain psionic creatures will not be detected by the party.

Modifying Psionics

A wish can create the potential to be psionic (assuming the necessary ability score of 16). A wish can also bestow immunity to one particular attack mode; immunity to all attack modes precludes using any disciplines.

As a character ages, their intelligence and wisdom also change.  Adjust the psionic strength.

The following mechanisms increase a character’s psionic strength (half to attack strength, half to defense strength). This strength will be spent before the innate strength, and recover at the same time as the psionic strength at the same rate:

  • The helm of telepathy increases psionic strength by 40 (in additional to providing a +4 to saving throws vs. Psionic Blast).
  • A dull gray ioun stone increases psionic strength by 10, to a maximum of 50 (e.g. 5 ioun stones)
  • Ioun stones which merely increase intelligence, wisdom, or charisma will not increase the creature’s psionic abilities, as psionic strength is determined by unmodified ability scores.

References

TSR 2010, Players Handbook [1e], 1978.
TSR 2011, Dungeon Masters Guide [1e], 1979.
TSR 2013, Deities & Demigods, 1980.
Dragon Magazine Issue 35, The official errata: Scads of additions & Revisions for AD&D. [Errata removes psionic elves]
Dragon Magazine Issue 39, Sage Advice. [Only humans, possibly dwarves and halflings]
Dragon Magazine Issue 42, Sage Advice. [Limit psionic elves to NPCs, MM]
Dragon Magazine Issue 58, Sage Advice. [Dwarves and psionics]
Dragon Magazine Issue 60, The Elven Point of View.  [Elves not psionic]
Dragon Magazine Issue 67, The Astral Plane, 1982. [EGG added elves psionic]
Dragon Magazine Issue 67, Featured Creatures, 1982. [potential for psionic valley elves]
Dragon Magazine Issue 71, Solid answers to astral questions. [Psionics and Astral]
Dragon Magazine Issue 78, Psionics is different.  [All PCs can be psionic, ability score changes]
Dragon Magazine Issue 78, Sage Advice.  [All PCs psionic, ability score changes]

 

Appendix A: Psionic vs. Psionic in Mental Combat (Short Range)

 

Attacker Psionic Strength Attack Mode Attack Cost Defense Cost (ordered by “best”)1,2
01-25 Psionic Blast 20 Mind Blank(4), MR(7),IF/TS(9)
01-25 Mind Thrust 4 Mental Barrier(3), TS(6), IF(8), TW(11)
01-25 Ego Whip 7 Mental Barrier(3), TS(5), IF(8), MB(9)
01-25 Id Insinuation 10 Mind Blank(2), TS(8), IF(9), MR/TW(11)
01-25 Psychic Crush 14 Though Shield(2), MR(3), IF(8)3
26-50 Psionic Blast 20 Mind Blank(7), MR(9),IF/TW(10)
26-50 Mind Thrust 4 Mental Barrier(4), TS/IF(8), MR(3)
26-50 Ego Whip 7 Mental Barrier, TS(6), IF(8), TW(10)
26-50 Id Insinuation 10 Mind Blank(3), TS(10), IF(11), MR/TW(13)
26-50 Psychic Crush 14 Intellect Fortress(8), TW(10), MR(3), TS(2)3
51-75 Psionic Blast 20 Mind Blank/Tower(11), MR/IF(12)
51-75 Mind Thrust 4 Mental Barrier(5), IF(10), TS(11),TW(13)
51-75 Ego Whip 7 Mental Barrier(4), TS(8), IF(9), TW(11)
51-75 Id Insinuation 10 Mind Blank(5), TS(13), IF(15), MR/TW(16)
51-75 Psychic Crush 14 Tower of Iron Will(10), IF(8), MR(3), TW(2)3
76-100 Psionic Blast 20 Tower of Iron Will(12), IF(15),MB/MR(16)
76-100 Mind Thrust 4 Mental Barrier(8), IF(12), TS/TW(15)
76-100 Ego Whip 7 Mental Barrier(6), IF(10), TS(11), TW(15)
76-100 Id Insinuation 10 Mind Blank(8), TS(17), Other(20)
76-100 Psychic Crush 14 Tower of Iron Will(10), IF(8), MR(3), TS(2)3
101-125 Psionic Blast 20 Tower of Iron Will(14), IF(19), MR(21), MB(22)
101-125 Mind Thrust 4 Mental Barrier(12), IF(15), TW(18), TS(20)
101-125 Ego Whip 7 Mental Barrier(9), IF(12), TS(15), TW(16)
101-125 Id Insinuation 10 Mind Blank(12), TS(22), MR/TW(25)
101-125 Psychic Crush 14 Tower of Iron Will(10), IF(8), MR(3), TS(2)3
126+ Psionic Blast 20 Tower of Iron Will (17), IF(24), MR(27), MB/TS(29)
126+ Mind Thrust 4 Intellect Fortress/MR(19), TW(22), TS(26)
126+ Ego Whip 7 Mental Barrier(12), IF(15),TS/TW(20)
126+ Id Insinuation 10 Mind Blank(17), TS(28), IF/TW(31)
126+ Psychic Crush 14 Tower of Iron Will(10), IF(8), MB(3), TS(2)3

 

1MB – Mind Blank, MR – Mental Barrier

2This table takes into account the sum of the defense mode cost and the damage cost.

3Calculations for Psychic Crush select the most efficient defense least likely to cause instant death.

 

Appendix B: Psionic vs. Psionic in Mental Combat (Medium/Long Range)

        Defense Cost1
Attacker Psionic Strength Attack Mode Cost Mind Blank Thought Shield Mental Barrier Intellect Fortress Tower of Iron Will
01-25 Psionic Blast 20   3 8 6 9 10
01-25 Mind Thrust 4 11 5 3 8 11
01-25 Ego Whip 7   7 4 3 8 10
01-25 Id Insinuation 10 2 7 9 9 11
01-25 Psychic Crush 14   1 2 3 8 10
26-50 Psionic Blast 20 6 9 8 10 10
26-50 Mind Thrust 4   13 7 4 8 12
26-50 Ego Whip 7 11 5 3 8 10
26-50 Id Insinuation 10   3 8 11 10 12
26-50 Psychic Crush 14 1 2 3 8 10
51-75 Psionic Blast 20   9 12 10 11 11
51-75 Mind Thrust 4 15 9 5 10 12
51-75 Ego Whip 7   15 7 4 9 11
51-75 Id Insinuation 10 4 11 13 14 15
51-75 Psychic Crush 14   1 2 3 8 10
76-100 Psionic Blast 20 13 15 13 14 12
76-100 Mind Thrust 4   19 12 7 11 14
76-100 Ego Whip 7 19 9 5 10 12
76-100 Id Insinuation 10   7 14 17 18 18
76-100 Psychic Crush 14 1 2 3 8 10
101-125 Psionic Blast 20   18 19 17 17 13
101-125 Mind Thrust 4 22 16 10 14 16
101-125 Ego Whip 7   25 12 8 11 15
101-125 Id Insinuation 10 10 18 21 22 22
101-125 Psychic Crush 14   1 2 3 8 10
126+ Psionic Blast 20 23 24 22 21 16
126+ Mind Thrust 4   25 21 16 17 20
126+ Ego Whip 7 31 16 11 14 18
126+ Id Insinuation 10   14 23 25 28 27
126+ Psychic Crush 14 1 2 3 8 10

1This table takes into account the sum of the defense mode cost and the damage cost.

Appendix C: Psionic vs. Defenseless Psionic

Defender’s Psionic Strength (Attack Strength + Defense Strength)
Attack Strength Attack Mode 10-59 60-109 110-159 160-209 210-259 260-309 310+
01-25 Psionic Blast D C C 15 10 5 5
01-25 Mind Thrust W W 40 35 30 25 20
01-25 Ego Whip 30 25 20 15 10 5 5
01-25 Id Insinuation 40 35 30 25 20 15 10
01-25 Psychic Crush 72% 60% 50% 40% 30% 20% 10%
26-50 Psionic Blast S D C C 15 10 5
26-50 Mind Thrust W W W 40 35 30 25
26-50 Ego Whip 35 30 25 20 15 10 5
26-50 Id Insinuation R 40 35 30 25 20 15
26-50 Psychic Crush 75% 62% 52% 42% 32% 22% 12%
51-75 Psionic Blast W S D C C 15 10
51-75 Mind Thrust P W W W 40 35 30
51-75 Ego Whip 40 35 30 25 20 15 10
51-75 Id Insinuation R R 40 35 30 25 20
51-75 Psychic Crush 79% 65% 55% 45% 35% 25% 15%
76-100 Psionic Blast P W S D C C 15
76-100 Mind Thrust P P W W W 40 35
76-100 Ego Whip P 40 35 30 25 20 15
76-100 Id Insinuation R R R 40 35 30 25
76-100 Psychic Crush 84% 69% 59% 49% 39% 29% 19%
100-125 Psionic Blast K P W S D C C
100-125 Mind Thrust P P P W W W 40
100-125 Ego Whip I P 40 35 30 25 20
100-125 Id Insinuation R R R R 40 35 30
100-125 Psychic Crush 90% 74% 64% 54% 44% 34% 24%
126 & up Psionic Blast K K P W S D C
126 & up Mind Thrust P P P P W W W
126 & up Ego Whip I I P 40 35 30 25
126 & up Id Insinuation R R R R R 40 35
126 & up Psychic Crush 97% 80% 70% 60% 50% 40% 30%

 

C             Confused for 2-8 rounds, Only non-psionic activity possible

D             Dazed for 1-4 turns, no psionic or other activity

I               Idiocy, psionic ability lost forever, idiocy only curable by a heal spell

K             Killed, raising/resurrection is possible, but psionic ability is lost

P             Permanent loss of random attack/defense/ discipline, and dazed as above

S              Sleeping in a coma for 1-4 weeks (catatonic state 99% likely to be mistaken for death)

R             Robot, mind is controlled by victor until released or after 2-8 weeks a saving throw versus magic

W            Wounded psionically. Randomly determine an attack/ defense/ discipline unusable for 2-8 weeks

 

A number result reduces the defender’s psionic strength, defense strength first. If the attack strength reaches 0, reduce the defender’s hit points by the remainder of the number.  Psionic creatures with mind bar discipline will take damage only on a segment after all psionic strength is lost, so treat letter results as a 40 until 0 is reached. If psionic strength is reduced beyond 0, treat it as hit point damage on a point-for-point basis.

 

 

Appendix D: Psionic Blast on Non-Psionics

Attacked Creature’s Total Intelligence and Wisdom Saving Throw Death Coma Sleep Stun Confuse Enrage Panic Feebleminded Permanent Insanity Temporary Insanity Mild Insanity
0-5 20 01-85 86-99 00 – – – – – – – –
6-9 18 01-10 11-90 91-99 00 – – – – – – –
10-13 16 01 02-15 16-90 91-99 00 – – – – – –
14-17 14 – 01 02-10 11-90 91-99 00 – – – – –
18-21 20 – – 01 02-15 16-90 91-99 00 – – – –
22-25 10 – – – 01 02-15 16-90 91-99 00 – – –
26-29 8 – – – – 01 02-15 16-90 91-99 00 – –
30-33 6 – – – – – 01 02-15 16-90 91-99 00 –
34-35 4 – – – – – – 01 02-20 21-85 86-99 00
36-37 2 – – – – – – – 01 02-15 16-90 91-00
38 & up 0 – – – – – – – – 01 02-15 16-00

 

DEATH:                                 Creature can be brought back to life as is usual.

COMA:                                2-12 days where creature cannot be awakened.

SLEEP:                                   5-20 turns where creature cannot be awakened.

STUN:                                   2-8 turns where character is at usual stunned condition (-3 on saves vs. psionic blast, +4 to hit).

CONFUSE:                           1-4 turns as per the spell of the same name.

ENRAGE:                             2-8 rounds and creature affected must immediately launch a spell or physical attack upon any opponent or other creature. During enraged period, creature will not think of defense or any action save attacking.

PANIC:                                  2-8 rounds with reaction as a fear spell from a 4th level magic user.

FEEBLEMIND:                     This lasts until a heal, restoration, or wish is used. The creature’s combined intelligence & wisdom is in the 0-5 range when so affected. All memory of spells is gone, and the affected creature cannot attack or defend.

1PERMANENT INSANITY: This lasts until a heal, restoration, or wish is used. Select two forms of insanity from the table therein, and have affected creature behave accordingly as long as the condition lasts.

1TEMPORARY INSANITY:               2-1 2 weeks duration, otherwise as above.

1MILD INSANITY:              1-4 weeks duration, one form of insanity only, otherwise as above.

1In most cases the fact that the creature has been inflicted with insanity will NOT be immediately evident to associates. Behavior will make the condition suspect as appropriate to the form of affliction.

What Do You Know?

Last updated: 210920…230313

The Player’s Handbook includes the Intelligence “Chance to Know” for Magic User and Illusionist spells. In short, Mages can’t learn some spells, determined based on their intelligence. Which doesn’t quite integrate with the DMG, UA or OA. Of course.

 

“Each and every magic-user character must employ the Table [for minimum and maximum number of spells /level] in order to determine which and how many of each group of spells (by level) he or she can learn.”, PHB, p. 10.

A “level group” includes all of the spells of a particular level. During character creation, the mage rolls the Chance to Know for the Level 1 level group. When the mage can cast Level 2 spells (i.e., a Level 3 mage), the mage rolls for the Level 2 level group, etc. The mage makes “a complete check of each spell in the level group” for Chance to Know, in the order of their choosing (see Maximum Number below however). Any spell that passes the Chance to Know roll will be able to be comprehended, learned, and memorized once acquired. Any spell that fails the Chance to Know roll likely cannot ever be understood by the mage (see Write and Change of Intelligence however).

The Minimum Number is a safety net for the rare case where too few spells could be understood. After all, what’s the fun of playing a mage who can only understand a single spell! If the minimum number isn’t reached after rolling Chance to Know for the entire level group, the player works through the list of spells that failed on the first pass (again, in any order they wish), checking one spell at a time until they reach the Minimum Number.

Some groups delay rolling Chance to Know until each individual spell discovery, but that’s flawed. The Minimum is the reason “one complete check” (PHB, p. 10) of a new level group is done, since if the minimum is not reached  any mage rolling below the minimum wouldn’t be able to recheck the level group until encountering all of the spells of the level group—an unlikely event!

 

The Maximum Number defines the spells that could be learned. As written, while rolling Chance to Know for a level group, If the maximum is reached, the character may not ever check any further in the level group (see Change of Intelligence). However, applying the Maximum to the Chance to Know roll for the level group creates significant issues, given that for the low-level spells the mage will mathematically almost certainly reach their maximum (even if you don’t roll for the UA spells) long before reaching the end of the spell group:

  • The mage won’t be able to create new spells (as they will have already reached their maximum on the initial Chance to Know roll).
  • If the mage discovers a “heretofore unknown” spell , they will already have reached their maximum, so be unable to even roll Chance to Know.
  • For a mage with a low intelligence, they will start with only 2-3 additional 1st level spells they can cast, and they have to find those specific spells. Even a mage with an 18 Intelligence will only have 14 Level 1 spells they can cast, so never even roll Chance to Know for the majority of spells they find.

The text itself is contradictory, as Maximum is also defined as the maximum a mage can have in their spell books. For me, I apply the Maximum only to those spells that have actually been learned (in their spell book, memorizable and castable). Check the entire level group; the mage can choose to learn on discovery what spells to learn, up to the maximum.

That also means that for all practical purposes, if the Minimum Number of Spells/Level is reached, the mage can stop checking, and check any remaining spells at time of discovery. It also prevents consigning mages with a lower Intelligence to a fate of seeking those missing spells—they can just decide, with each spell the find, whether to add it to their list of learned spells (after checking Chance to Know).

The 1st Level Mage

The intelligence of the mage dictates which spells can be known (DMG, p. 39). The 1st Level mage first rolls Chance to Know for the entire level group of 1st level spells. They then add to their spell book Read Magic and three additional spells randomly selected by the DM (although on a roll of “0” the player may choose). Obviously, an apprentice must know Read Magic to be of use to his master—they cannot fail this roll. At the same time, Read Magic is one of the minimum number of spells that can be comprehended, as well as counting towards one of the maximum number of spells learned.

The three additional spells is defined with flexibility, as:

“If your campaign is particularly difficult, you may wish to allow choice automatically. You can furthermore allow an extra defensive or miscellaneous spell, so that the character begins with 5 spells.” DMG, p. 39.

As the mage defaults to four spells to seek their fortune, if a roll to determine those three additional spells specifies a spell that can’t be comprehended (due to a failed Chance to Know roll), the spell category (offense, defense, misc.) should be rolled again. That aligns with “While the intelligence of the player character will dictate how many and which spells can be and are known, this knowledge is not automatic” (DMG, p. 39) and incorporates the illusionist “ignoring any rolls that result in duplication”; rolling again is the simplest solution. Certainly the intent is not to have a mage without usable spells in their starting spell book!

The illusionist originally followed a different process than the magic-user for starting spells, rolling d12 against the entire 1st level illusionist level group (rerolling duplicates), with the DM allowing an additional one to two spells for a difficult campaign (DMG, p. 39). UA aligned that process to the magic user, rolling on a table of offensive, defensive, and misc. spells, expanded to include UA spells (UA, p. 80).

Acquiring New Spells

Mages acquire new spells from three sources: one spell upon gaining a level, discovery of scrolls and spell books, and spell creation. The Maximum Number of Spells/Level comes into play whenever acquiring new spells.

“…it is possible to acquire knowledge of additional spells previously unknown as long as this does not violate the maximum number of spells which can be known.” (PHB, p. 10).

Any future spells discovered that have not yet had Chance to Know determined are considered unknown (see Spell Discovery), and are checked at time of discovery if the mage has not reached their Maximum Number of Spells / Level.

 

There’s no exception defined for a mage that has reached their Maximum: “As soon as this maximum is reached, the character may not check any further in the level group” (PHB, p. 10). That said, it’s easy enough to house rule the mage can drop a spell. We play that to learn a spell —in the rare case that Maximum Knowable has been reached—the mage loses one spell at random. A more lenient style would permit the player to choose the spell to be lost.

Gaining a Level

When a mage gains a new level beyond the first, two things happen. If they’ve gained access to a new level group, they check Chance to Know for all of the spells of that level group to confirm minimum (and likely maximum) spells. They also gain a new spell (DMG, p. 39).

Polyhedron #30 (JUL 1986) article DISPEL CONFUSION wrote:

“It is up to the individual DM to determine whether new spells are assigned or given by choice in a particular campaign. In either case, the “chance to know” roll still applies, and the character may or may not be given a chance to choose another spell if the first offering call not be learned. Also, the DM may choose to make only certain spells available through the training process, so the choice may be limited.”

Where does that spell come from when they gain a level? The DM can certainly allow a player to select any spell upon leveling (effectively, creating it). However, the rules for spell creation, which involve money, time, a library, and a chance of failure don’t align with the timeframe and costs for training. Gygax (Dragon, January, 1980) also states:
“even if a spell-caster is capable of knowing/memorizing many and high-level spells, he or she must find them (in the case of Magic-Users and Illusionists) or have the aid of deities or minions thereof (in the situation faced by Clerics and Druids)” and “The ramifications of spell scarcity are bound to aid your campaign.” Spells should be hard to acquire, and don’t just appear ready-to-use.

The trainer providing a scroll, or a spell from their own spell book, is more consistent with those philosophies than the player just choosing what they want. The trainer could, of course, offer his student a choice of the spells within his spell book. Or not. That leaves open where the mage acquires the spell when leveling without a trainer/tutor—a scroll acquired as part of the increased training cost is one explanation.

Spell Discovery

As long as the mage hasn’t learned their Maximum Knowable spells for the spell group, they can learn additional spells.

When a mage discovers a spell they can comprehend (determined by the earlier Chance to Know) in a spell book or scroll, they can add it to their spell book (after casting Read Magic to know that they know it!). Transcribing a scroll into a spell book requires one day for each spell level (e.g., a 3rd level spell takes three days) before the spell can be memorized.

When the mage discovers a heretofore unknown spell that has never had the Chance to Know rolled, and has not reached their Maximum, they roll the Chance to Know. Success means they can comprehend and learn the spell. How could they encounter a spell without a previous Chance to Know roll? That spell could be a unique spell created by a module or campaign, or was otherwise previously unavailable. As an example, my campaigns don’t check the UA spells at character creation; when a UA spell is discovered, the mage determines Chance to Know.

Creating New Spells

The mage can also research new spells by creating them (DMG, p. 115). Whether the spell is new, or a listed spell the character has been unable to locate during the course of adventuring, the mage can attempt to create the spell as long as they have not reached the Maximum for that spell group.

The player presents to the GM the specifics of the desired spell, after which the GM determines the spell level (DMG, p. 115). If the GM determines the spell level is above the level the mage can cast, research is possible, but useless. If the spell caster doesn’t spend enough money on research, there will never be success. In either case, there will be no indication that their attempt is fruitless. The DMG instructs that the player will be unaware of the specifics of the calculation. Even if the spell creation is impossible, the DM should still permit them to keep throwing their gold away week after week until they give up. For a game 40+ years old, that’s unlikely and impractical—the GM and player should be in accord for the spell level. At the very least the GM should permit the mage to consult a sage to determine spell level.

With access to a library within one day’s travels (or a shrine, in the case of a cleric), researching a new spell requires a minimum number of weeks equal to the determined spell level. Any day of interruption will set progress back one week. The research cost for each week will be:  a base cost of 200 gp / spell level per week + a variable 100-400 gp / spell level each week for materials. If no library is at hand, the base cost increases by a factor of 10 (from 200 gp to 2000 gp)!  After the minimum research period, the base chance of creating the spell that week (and each week thereafter) is 10%, modified by intelligence, mage level, and spell level:  ((10 + Intelligence + mage level) – (2 × spell level)))%.

For each additional 2,000 gp spent per spell level, the base chance can be further increased by 10%, (i.e., for a first level spell an additional 2,000 gp/spell level for a 20% base, and additional 4,000 gp for a 30% base, an additional 6,000 gp for a 40% base, and an additional 8,000 gp for a 50% base (the maximum)).

Unearthed Arcana

Unearthed Arcana defines a heretofore undefined capacity for spell books. A standard spell book, with an encumbrance of 450 gp) is composed of 72 pages of thick vellum, and can contain only a limited number of spells—spells of levels 1-3 use three pages each, spells of levels 4-6 use six pages each, and spells of the levels 7-9 require nine full pages each.

UA also adds the spell and requirement of the 1st level Read Magic to the Illusionist, and a table for the initial illusionist spells, making the illusionist spell process virtually identical to the magic user.

Write

The Write spell will: “inscribe a spell he or she cannot understand at the time (due to level or lack of sufficient intelligence) into the tome or other compilation he or she employs to maintain a library of spells.”

Write conveys no additional abilities. Mages can’t automatically comprehend spells inscribed in a spell book; that’s superseded by the Chance to Know roll.

Combining Write with UA, Write could inscribe a spell into a spell book, to later be cast, in extremis, just as if the spell book were a scroll. But that still doesn’t negate the Chance to Know—UA requires the spell to be knowable in such a circumstance (differing from casting an unknowable spell from scroll, which is permitted (DMG, p. 128)).

Change in Intelligence

“If intelligence goes down or up for any reason, and such change is relatively permanent, the magic-user must check again as explained above for known spells by level group.”

On first glance, a change in mage intelligence completely randomizes their spell selection. However, a closer read shows “for known spells”. If the Intelligence decreases, OA states that Chance to Know is checked for known spells until enough spells are forgotten to comply with a new Maximum. The wise mage will first check those spells that passed Chance to Know buy have yet to be discovered!

On increase, the mage begins their check anew, re-checking each level group in the order of their choosing for additional spells until they have reached their new Maximum.

Oriental Adventures

OA includes a number of statements in the context of the wu jen, all more definitively stated than the original text in the PHB:

  • Chance to Know is checked for every spell at the time the mage gains access to a new spell group.
    • If the Minimum is not reached, start checking again, one spell at a time, until the Minimum is reached.
    • If the Maximum is reached while checking Chance to Know, stop.
  • If a spell that has not failed Chance to Know is encountered “in the field”, the mage can check Chance to Know if not at Maximum.

References

 

TSR 2010, Players Handbook [1e], 1978.
TSR 2011, Dungeon Masters Guide [1e], 1979.
Dragon Magazine, Issue 33, “Sorceror’s Scroll: AD&D’s Magic System: How and Why it Works,” January, 1980.
TSR 2017, Unearthed Arcana [1e], 1985.
TSR 2018, Oriental Adventures [1e], 1985. p. 25. [Not quite identical to PHB]
Dragon Magazine, Issue 139, “Sage Advice,” November 1988.
Dragon Magazine, Issue 147, “Spelling it Out,” July, 1989. [Not consistent with RAW]

A Skilled Conversion of Proficiencies

Last Updated: 210914..230107

I have a love/hate relationship with Proficiencies. Proficiencies can be a great way to add flavor to a PC. Yet when comparing proficiencies to Class abilities, proficiencies are disproportionately effective (initial thief functions are only 25%). The very word—”proficient”—implies a high level of success.

The proficiency system in 1e biases heavily towards high stats. 1e uses a class-based system, but should all classes be equal for the same proficiencies? There’s no explicit adjustment for tasks of varying difficulty. Proficiencies don’t advance with experience. To exemplify the issue that proficiencies aren’t quite right, each edition uses a different system. Even 1e uses more than one system (Oriental Adventures *cough*).

Here’s an alternate skill system derived primarily on the Dragon Magazine #225 system, and vaguely similar to OA with different checks. Skills are weaker to start, but improve as a PC levels.

A character starts with a certain number of skills, which can be improved or expanded upon as the character levels. When performing a skill check, the player rolls a d20, and is successful if they roll equal to or less than the target number. Skill checks are modified for the difficulty of the task, but difficulty of the task is determined based on the PC’s skill level.

  • Standard proficiency slots per class + Intelligence bonus determine Skill Slots available to acquire or improve new skills.
  • A specific skill provides a base 10 target number +/- a skill modifier, representing the intrinsic difficulty or simplicity of that particular skill (e.g., Alchemy, based on Intelligence, has a -3 target number penalty, i.e., a base target number of 7).
  • The ability score associated with the particular skill modifies the target number:
Ability score modifier
12 +1
13 +1
14 +1
15 +2
16 +2
17 +3
18 +3
  • Non-Fighters have a -1 penalty on STRENGTH proficiencies, and a +2 max bonus on CONSTITUTION skills (aligning Strength checks more closely to the ability tables).
  • Learning a skill that mimics a class skill from another class incurs an additional -6 target number penalty.
  • Multi-class characters start with a number of skills equal to the total proficiency slots from both classes, and earn new skill slots at the proficiency rate of the fastest class.
    • Specializing in a skill (using an additional slot) improves the base target number by 3 (journeyman).
    • Double specializing (spending two additional slots) will improve the skill target number by an additional 2 (master). Further specialization will improve the skill target by 1 for each additional point spent.
  • Each level the PC gains 1 additional point to improve/increase one previously-selected skill’s target number of their choice by 1 point (multi-class characters get 1 each time they reach a new highest level).
    • The player must choose which skill will be modified upon gaining the new level.
    • Unlike gaining new slots, the experience modifier may not be saved from level to level. If they are not assigned, they are lost.
    • The player may select any of the character’s previously-selected skills to improve. The only restriction on this choice is that a newly-acquired skill cannot be chosen.
    • The skill target number is then modified further by the associated ability score.
  • Attempts can be made against an unlearned skill, with base target number of 0.
  • When two characters with the same skill work together on the same task, use the score of the player with the best skill (the one with the greatest chance of success). Furthermore, a minimum of +1 bonus is added for the other character’s assistance (+1 for each additional point they have added to the skill). The bonus can never be from more than 1 PC; too many assistants are sometimes worse than having none.
  • To determine success, Roll d20 <= the modified target number based on the difficulty of the particular task for someone who knows the skill:
Modifier to Target number
Easy +5
Average 0
Hard -5
Very hard -10
Nearly impossible -15
  • Always fail on a 20. Success on a 1 is not guaranteed.
  • When there are opposed skill checks, use the delta of success to determine success.
  • Where applicable, acquiring a skill conveys the initial expectation of apprentice-level ability, not mastery. In other words, determine the difficulty as if the PC was an apprentice, not a master. If the PC has spent 2 proficiency slots, then determine difficulty as if the PC were a journeyman, and 3 (or more) slots as if they were a master.

Optional*

Buying a non-class skill costs 1 more slot. Class skills are a combination of DRMG 225 and 2e, leaning towards permissive.

F Fighter Paladins are also Clerics, Rangers are also Magic Users, Barbarians are also Thieves
M Magic User  
C Cleric Druids are also Fighters
T Thief  
B Bard  
K Monk Monks are also Thieves

*I apply this only to skills that replicate class-like abilities.

Bibliography

TSR 2018, Oriental Adventures [1e], 1985.
TSR 2019, Dungeoneer’s Survival Guide [1e], 1986.
TSR 2020, Wilderness Survival Guide [1e], 1986.
Dragon Magazine, Issue 224, “Back in the Saddle (Again) January 1996.

Another Surprising Detail

Last Revised: 221102..251212

From previous analysis, the elf ability to Surprise on 1-4 in d6 when not in metal armor and 90′ in advance derives from +1 from being hidden, and +1 from being silent. That’s consistent with the PHB example—a party moving silently and invisibly is +2 to their chance to Surprise (see also Polyhedron #133).

But does the elf adjustment derive in any way from being hidden? From the PHB: “If alone and not in metal armor … an elven character moves so silently that he or she will surprise monsters [1-4 in 6].” There’s no mention of being hard to see. From the MM entry for the elf: “When in natural surroundings such as a wood or meadow, elves can move silently (surprise on a 1-4) and blend into the vegetation so as to be invisible (requiring the ability to see invisible objects to locate them) as long as they are not attacking.” Again, their (improved) ability to Surprise is specifically attributed only to silence. Both the elf and halfling also lose their +2 to surprise if they have to open a door, where the noise from a door is attributed to a noisy failed attempt (DMG, p. 62).

Silent + invisible improves surprise to 1-4 in d6. The thief “Move silently” is only “little sound and disturbance”, not “completely silent”.  Could the elf be, well, extra silent? Bugbears (“silent creatures”, “with great stealth”, “will never be heard”) only add +1.   Yet there’s support for “extra silent” enhancing Surprise. The giant owl flies “with nearly absolute silence, thus it surprises on 1-5 (on a 6-sided die).” Unicorns “move very silently and surprise opponents on a 1-5.” With the ring of the faerie the wearer’s move silently alone enables surprise on a roll of 1-4 on a d6.

 

There are other creatures that surprise on 1-5 with improved hiding: The huge spider, attributed to some combination of carefully hidden places and leaping; the xorn blending into stone; the giant lynx “hide themselves”. The invisible stalker surprises on 1-5 in 6, which isn’t attributed to anything (although clearly “invisible” is part of it).

Clearly it’s possible to improve the chance to surprise by being extra hidden or extra silent. Potentially blending into the background of the world so well as to be more hidden than invisible, and more silent than total silence. In a way that makes sense—an absence of noise is, in and of itself, noticeable.  An invisible character still leaves traces in the dust on the floor and air (and infrared footprints on the ground!).

But is the elf specifically not hidden? Digging deeper, UA ascribes the elven ability to hiding: “[Solonor] taught the first elves the art of hiding in and moving through natural foliage so as not to be detected” suggests attributing some elven ability hiding.  Looking at the MM halfing: “exceedingly clever at both quiet movement and hiding … surprise on a die roll of 1-4 on a 6-sided die. In natural terrain they must be treated as invisible if they have any form of vegetation in which to conceal themselves.”  Very similar to the elf description(s), except that the quiet movement and hiding are both attributed to their ability to surprise. The elven surprise ability can be assumed the same as the halfling, since they can travel together and maintain their enhancement. So either the elf ability is silent + hidden, or the halfing is also extra silent.

From the above, if the elven ability to surprise does not include hiding, they’re:
+1 to Surprise because they’re silent
+1 to Surprise because they’re an elf (and extra silent)
which means an additional +1 if they’re somehow hidden as well—a significant increase in the elf’s ability to surprise. If invisible, or in natural surroundings, the elf would surprise 1-5 in 6, surprising 61% of the time, 42% of the time for 3 or more segments.

So does the elven ability not include being hidden? Elves have almost the same enhancement to Hide in Shadows (+10%, +15% for halflings).  Assuming the elven ability derives only from silence ignores indirect references to their being hard to see. However, to my mind most significant is that both halfling and elven abilities include the ability to be “hidden”/”as to be invisible”/”hiding”. If they are “extra silent” their surprise ability would more accurately be presented as 1-5 in 6, and it’s not. I’m sticking with +1 hidden, +1 silent. It’s an interesting approach however, significantly modifying Surprise in the party’s favor.

References

TSR 2010, Players Handbook, 1978.
TSR 2011, Dungeon Masters Guide, 1979.
TSR 2017, Unearthed Arcana, 1985.
Polyhedron #31, “Dispel Confusion”, 1987, p. 31.

Potion Creation

Last Updated: 221011…240621

(This article has been supplanted by The Alchemy of Potions)

How do PCs create potions? For years I’ve assumed there’s two stages: a) the mage researches the formula, b) the mage creates the potion. But is that really how it works?

In addition to the Alchemist expert hireling in the DMG, Dragon magazine includes not one but four different variations of the alchemist (#002, #046, #049, #130). The alchemist is also discussed in the 2e Player’s Options (Skills & Powers, Spells & Magic). Several include the research component:

  • Dragon #002: “Research costs are the same as MUs for Spells”
  • Dragon #130: “The DM adjudicates the alchemist’s success in research. The costs for research is at least 50-300 GP per level of the potion desired.”
  • Skills & Powers: “The alchemist must first research the potion’s formula, as if conducting normal spell research.”

Yet per the DMG: “In order to find out [how to fabricate magic items], they must consult with a sage (q.v.) or a high level character of the proper profession, the latter being detailed a bit hereafter.” where the only item that requires consulting with someone “of the proper profession” is potion creation and the alchemist. The only requirement for a 7th level magic-user (or presumably 7th level cleric in the case of healing potions) to concoct a potion is hiring an alchemist (and even that requirement is removed when the magic-user reaches 12th level).

So, the magic-user needs:

  1. an alchemist
  2. a lab/workshop
  3. the appropriate special ingredient
  4. manufacturing

An Alchemist

Hiring an alchemist will cost a 10d10 GP hiring bonus plus assurance of 300 GP / month for a minimum of 1 year.

Lab/Workshop

Initial outlay for the creation of a workshop costs 200- 1,000 GP, based on the relative availability of the tradesmen and goods necessary to complete the work room and stock it properly (and keep it stocked). In addition, upkeep of the laboratory requires a further monthly outlay of 10% of the total cost of the place, exclusive of any special provisions or protections, in order to stock basic fuel and supplies, replace broken equipment, and so on when the laboratory is in use.

The Appropriate Special Ingredient

There are lists of suggested special ingredients in the DMG (pp. 116-117) and Dragon #130. Per the DMG, there’s no need to figure out what the special ingredient is. Some overly complicated math suggests that the average cost of the special ingredient, if available on the open market, would be 24% of the GP value of the potion. Otherwise, it’d be up to the PCs to acquire.

That said, I really like the idea of specific formula determination as a rate limiter on potion creation. That research would require 1d3+1 weeks at a cost based on the potion’s XP value per week (in addition to any costs for an alchemist), but if the character uses a commune or contact other plane spell to speed his research, they automatically succeed in the minimum time. Otherwise, at the end of this period, successful potion creation requires a roll as per the chance to learn a spell, -2% for each 100 XP (or fraction thereof) of the potion. If the character has a full dose of the potion in question to use as a sample, the research takes one less week with no penalties. If unsuccessful, research continues week-by-week until successful.

Manufacturing

Both the cost in gold pieces and the days of compounding are determined from potion’s XP (default 200 XP otherwise). The XP for a given potion is the cost in GP to concoct the basic formula sans the special ingredient. Each hundred XP (or fraction thereof) indicating one full day of compounding time to manufacture the liquid, i.e., 250 XP = 250 GP basic costs and 3 full days of time. The cost of the special ingredient if available: 24% of GP cost of potion in the DMG.

The DMG suggests: “Alternatively, a 5% to 20% failure percentage can be assigned to all potion manufacture, and those which are failures become delusion potions of the sort which was being attempted, i.e., animal control, flying, etc.” where you either require a special ingredient, or assign a chance of failure.

Where’s the fun in automatic success? So instead, let’s assign that range of failure: 2% for each 100 XP (or fraction thereof). What happens when upon failure to create a potion? The DMG suggests that these failures are simply the source of the potion of delusion, but that’s uninteresting. The Potion Miscibility Table provides some guidance, and can be readily adapted by adapting the wording (see also Dragon #130):

 

Failure

01 EXPLOSION! Those in a 10’ radius take 4-24 hit points, no save.
02-03 A poison gas cloud of 10’ diameter results, and all within it must save versus poison or die.
04-08 Mild poison which causes nausea and loss of 1 point each of strength and dexterity for 5-20 rounds, no saving throw possible.
09-25 Potion ruined and inert.
26-35 Potion at 50% normal efficacy.
36-90 Ruined (potion of delusion).
91-99 Potion has 150% normal efficacy (determine if both effect and duration are permissible, or if only the duration should be extended.).
100 DISCOVERY! The potion’s special formula will cause its effects will be permanent upon the imbiber with potentially harmful side effects.

 

Summary

  • Alchemist: 10-100 GP hiring bonus + 300 GP / month for a year
  • Lab: 200-1000 gp + 10% / month (for a year)
  • Research: d3+1 weeks at XP value / week
  • Manufacturing: Requiring 1 day for each 100 XP (or fraction thereof), at a cost in GP of the XP value, +25% of the GP value of the potion (the special ingredient).
  • Failure: 2% per each 100 XP.

Bibliography

TSR 2011, Dungeon Masters Guide [1e], 1979.
Dragon #2, August 1976. “A new D&D Character Class: The Alchemist”.
Dragon #45, January 1981. “…and one who seems the perfect mix”.
Dragon #49, May 1981. “A recipe for the Alchemist”.
Dragon #130, Feb., 1988. “Better Living Through Alchemy. Poison and Potions: The alchemist NPC class”.
Player’s Option:  Skills & Powers, 1995.
Player’s Option: Spells & Magic, 1996.

Casting About

 

At 10th Level (Master Thief), thieves are able to decipher magical writings and utilize scrolls of all sorts, excluding those of clerical, but not druidic, nature. However, the fact that thieves do not fully comprehend magic means that there is a 25% chance that writings will be misunderstood. Furthermore, magic spells from scrolls can be mispronounced when uttered, so that there is an increasing chance per level of the spell that it will be the reverse of its intent (PHB, p. 27)

I’ve got two thieves approaching level 10—it’s time to refresh myself on thieves casting from scrolls. To translate the above, 10th+ level thieves can read magic user, illusionist, and druidical spells, in addition to the Protection scrolls usable by any class (DMG, p. 128: “Protection scrolls can be read by any class or race of character even without a magic spell”).  While Intelligence can limit spell casting, “Those characters able to read and employ scroll spells may do so regardless of other restrictions” (DMG, p. 128), so the Intelligence of the thief doesn’t limit the level of spells .

The level that rangers and paladins cast a level 1 spell can be a bit confusing (“Does my Level 9 paladin cast Level 1 cleric spells as Level 1, or Level 9?”) but there’s no such question for scrolls. Unless specified otherwise, the scroll will function as a caster 1 level higher than required to cast the spell for the associated class, but at least 6th level (DMG, p. 128). A fireball (Level 3) can be cast as a level 5 magic-user, so will cast as if by a level 6 magic-user (which is also the minimum, i.e., Level 1 and Level 2 magic-user spells will also cast as if by a level 6 magic-user).

So the only thing left is “There is a 25% chance that writings will be misunderstood, and [an increasing chance of a reverse effect].”  We have only one source for chances of magic spell failure:

DMG, pg. 128: Magic Spell Failure: If a spell-user acquires a scroll with a spell(s) of a level(s) not yet usable by the character, the spell-user may still attempt to use the spell; the chance of failure, or other bad effect, is 5% per level difference between the character’s present level and the level of magic use at which the spell could be used. [Any score that represents failure then uses the following table]

Level Difference Total Failure Reverse or Harmful Effect
1-3 95% 5%
4-6 85% 15%
7-9 75% 25%
10-12 65% 35%
13-15 50% 50%
16 and up(a) 30% 70%

(a) Aside: Why isn’t just 16-17? Even assuming 0-level casters, 16-18?

For other spell-users, the chance of magic spell failure is “5% per level difference between the character’s present level and the level of magic use at which the spell could be used”. For the thief, it’s a flat 25% (“there is a 25% chance that writings will be misunderstood “). That makes a strange sort of sense, since the thief doesn’t have a difference in “level of magic use at which the spell could be used” since it’s always Level 10. The implication of Magic Spell Failure is that failure is determined at the time of reading the scroll—the thief won’t know if they will be successful until they attempt to use the scroll. And once they read the scroll to release its magic (successful or not), the writing completely and permanently disappears from the scroll (DMG, p. 128).

But that still leaves the question of how to determine the “increasing chance per level of the spell that it will be the reverse of its intent.” The Magic Spell Failure Table uses the Level Difference to determine the chance of a reverse effect. However, all levels of spell are theoretically accessible by the thief; at 10th level they can utilize “scrolls of all sorts”. Are we back to the paladin/ranger conundrum? However, the thief’s chance of reversal is tied to spell level, not character level. We also don’t consider the thief level for chance of failure—why would we use it for chance of reversal?

Now with no By-the-Book reference, how then to determine the  chance of reversal? The most extreme chance of reversal on the Magic Spell Failure Table is 70%. We can expect that even level 1 spells have a chance of reverse effect for the thief. Using the Magic Spell Failure Table for inspiration, we can come up with several methods to determine the chance of a reverse effect upon failure:

Spell Level Method: Level Difference Actual Reverse Frequency Method: By 5% Actual Reverse Frequency Method: By 10% Actual Reverse Frequency
1 5% 1.25% 5% 1% 10% 3%
2 5% 1.25% 10% 3% 20% 5%
3 5% 1.25% 15% 4% 30% 8%
4 10% 2.50% 20% 5% 40% 10%
5 10% 2.50% 25% 6% 50% 13%
6 10% 2.50% 30% 8% 60% 15%
7 15% 3.75% 35% 9% 70% 18%
8 15% 3.75% 40% 10% 80% 20%
9 15% 3.75% 45% 11% 90% 23%

Actual Reverse Frequency (above) is the calculated likelihood of a reverse effect occurring each time a thief uses a scroll (e.g., 25% chance of failure × 10% chance of reversal = 2.5% chance of the reverse effect occurring). From there we have to consider what was intended. Should a thief have, worst case, a 3.75% chance of a reverse effect when using a 9th level scroll? Probably not. 11% still seems too low. But a 23% total chance of a 9th level spell occurring in reverse seems reasonable, and comes close to maxing out the base chance of spell reversal at 90% (and appropriately worse than the 70% for reverse effect for the Magic Spell Failure Table). That leaves us with the following table:

Thief Spell Failure
Spell Level

Chance of Failure

Chance of Reversal
on Failure
1 25% 10%
2 25% 20%
3 25% 30%
4 25% 40%
5 25% 50%
6 25% 60%
7 25% 70%
8 25% 80%
9 25% 90%

Now that that’s settled (inasmuch as it can be), should the thief be able to cast spells from any spell book? “In extremis, the DM may allow a magic-user to cast a spell directly from any sort of spell book just as if the book were a scroll” (UA, p. 80). The thief can only explicitly “utilize scrolls”, and the ability to cast a spell directly from a spell book is an ability granted to the magic-user “as if it were a scroll”—not that spell books are scrolls. So no.

For assassins, tertiary functions of assassins are the same as thieves, performing thieving at two levels below their assassin level (PHB., p. 29; UA, p. 13). So 12th Level assassin functions the same as a 10th level thief. And, like the thief, their ability to read scrolls never improves.

 

No rule is completely worthless; it can always serve as a bad example

Last updated: 220220..250903
worthless@corwyn.net

Whenever rules are confusing, one normally turns to the examples to figure it out. In AD&D, don’t rely on it. Many of the examples contradict the rules as written. Indeed, using a baseline of, “the example is how not to do it” will sometimes serve in better stead.

Let’s look at some … examples.

MM, p. 30: “With a shout the party strikes with a general bonus of +3 to hit. They all succeed, and the halfling thief gains quadruple damage bonus of striking from behind!”

No mention of the thief’s +4 bonus for striking from behind. And the thief’s damage multiplier comes only with surprise (DMG, p. 74, “Thieves and assassins quadruple damage from a surprise back stab“).

 

PHB, p. 9: “If a character could normally carry 500 gold pieces without encumbrance, but the character had strength of 17 instead of the normal 8-11 range, 1,000 gold pieces could be carried without incurring movement penalty.”

From this quote, one might infer that the baseline for an average PC is 500 gp (50#). Yet that’s contradicted everywhere else. The PHB (p. 100) defines how movement is affected by encumbrance as: ≤ 35#, ≤70#, ≤105#, more than 105#. No 50# as part of the range. While WSG and DSG meddle a bit with the lower range of encumbrance (mostly adding a new classification of Unencumbered in the context of swimming), they still use 35/70/150 as the break points. OA meddles with the upper range of encumbrance, defining each 35# as a 3″ decrease in movement.

PCs don’t default to a base 50# of “free” encumbrance.

 

PHB p. 10: “Example: A character with an intelligence of 12 desires to know a charm person spell that he finds in a book or scroll, percentile dice are rolled, but the number generated is 52, so that spell is not understood and can not be used by the character.”

From this, one might interpret that one does not check Chance to Know Each Listed Spell until the spell is actually encountered. However, according to Minimum Number of Spells/Level, “If one complete check through the entire group fails to generate the minimum number applicable according to intelligence score, the character may selectively go back through the group, checking each spell not able to be learned once again. This process continues until the minimum number requirement has been fulfilled.” There’s only two ways there’s a complete check through the entire spell group (all the spells of that particular level): You check the entire spell group when gaining access (by leveling) to the spell group, or you only use Minimum Number after the mage has actually encountered all the spells of the spell group and not reached the minimum. Given the typical mage will never encounter all the spells of a spell group, checking Chance to Know until at least the Minimum is reached is the only practical implementation of the Minimum Number. Later text in the PHB confirms checking the entire list—”Although the magic-user must immediately cease checking to determine if spells are known after the first complete check of each spell in the level group”— as otherwise there’d be no need to immediately cease.

 

PHB, p. 12: “The wicked necromancer polymorphs (others) his hireling into a giant roc, with the rather foolish agreement of the changee; the hireling must make a saving throw based on his constitution score using the table above.”

While the text here states, “saving throw”, the clear intent is a System Shock roll, not a saving throw. If polymorphed, a PC would make a saving throw against the spell, and then a System Shock check to determine if changing form killed them. In this case, the hireling has agreed, so must only make a System Shock roll.

 

PHB, p. 34: “Let us suppose that a 10th level fighter has 55 hit points, plus a bonus of 30 hit points for his constitution, for a total of 85 hit points.”

and the corresponding example in the DMG, p. 82:

“Consider a character who is a 10th level fighter with an 18 constitution. This character would have an average of 5.5 hit points per die, plus a constitution bonus of 4 hit points, per level, or 95 hit points!”

Doing the math there, the PHB 10th level fighter has a 17 Constitution, gaining +3 hp/ level for 10 levels. The DMG fighter is calculated based on a 5.5 average of 10 hit dice + 40. However, the Constitution HP bonus applies to Hit Dice, not level.  The maximum number of Hit Dice are defined for each class on PHB, p. 19, Character Classes Table I and fighters stop gaining hit dice at level 9.

To support that, the PHB, p.  12 reads: “Hit Point Adjustment indicates the subtraction from or addition to each hit die for a character… the additional hit points for each hit die due to superior constitution is +2″ and further repeatedly emphasizes it on p. 19:
“**The ranger beings with two eight-sided hit dice (2d8), but thereafter goes up one die per level, to the indicated maximum, as do all other classes. The monk begins with two four-sided dice (2d4), and goes up thereafter as do rangers, at one die per level.”

“Maximum Number of Hit Dice assumes that the character has no racial limitation to prevent rise commensurate with the number of hit dice. Note that additional hit points are still gained with increase in level, even though no additional hit dice can be, in those cases where there is no class (or race) level limit. ”

That’s additionally supported in Dragon #144: “Q: Do characters still get constitution bonuses to their hit points after reaching “name” level? A: No. Once the character stops gaining new hit dice, he also stops gaining constitution bonuses.” and the Cavalier text in UA, p. 14: “The character’s hit-point bonus for high constitution (if applicable) is first received at either Horseman or Armiger level, and is then applied to each additional hit die from second level on as normal.”

Both examples erroneously assume fighters gain 10 hit dice, not 9. The PHB and DMG fighter should have a Con bonus of 27 (9×3) hit points, not 30!

 

PHB, p. 44: “Detect Evil: This is a spell which discovers emanations of evil, or of good in the case of the reverse spell, from any creature or object.”

However, the DMG (p. 60) goes on to say:

“It is important to make a distinction between character alignment and some powerful force of evil or good when this detection function is considered. In general, only a know alignment spell will determine the evil or good a character holds within. It must be a great evil or a strong good to be detected. Characters who ore very strongly aligned, do not stray from their faith, and who are of relatively high level (at least 8th or higher) might radiate evil or good if they are intent upon appropriate actions.”

Detect Evil won’t work on characters unless they are at least 8th level.

 

PHB, p. 105: “A party of 5 characters – a magic-user, a cleric, a thief, a human fighter, and a dwarf fighter surprise an illusionist with 20 arcs. The opponents are 30′ distant, and the magic-user immediately begins casting a sleep spell. The cleric also prepares to cast a spell, silence, 15′ radius. Meanwhile, the thief darts to the rear of the party to attempt to hide in the shadows and attack from behind when opportunity presents itself; the human fighter nocks an arrow and shoots it at the illusionist; and the dwarf hurls an axe.”

The party has surprise (which, while unspecified, must be for one segment given the example). The fighter nocks an arrow and shoots it.  However,

DMG, p. 63: “Even if distance prevents striking with weapons, the discharge of arrows, bolts or hand-hurled weapons is permissible at three times the normal rate providing the weapon/missiles are ready, otherwise at normal rates for rounds. Once surprise segments are over, melee proceeds normally on a round-by-round basis.”

Even if our fighter wasn’t ready, he should have fired two arrows, not one. Were he ready, he should have fired more. How many more is a different discussion.

 

PHB, p. 105: “The illusionist/orcs win initiative, and while the former begins a spell of his own, the latter rush to attack, hurling spears as they come. A spear hits the magic-user, so the sleep spell is spoiled.”

How exactly is the Sleep spell spoiled? Sleep takes but 1 segment to cast, and the magic user began (and completed) casting that spell during their 1 segment of Surprise (see above):

PHB, p. 103: “… magic spells require the proper number of segments of casting time, regardless of surprise.”

DMG, p. 61: “Most spells cannot be cast in a single segment, although first level magic-user/illusionist spells are usually but 1 segment long, as are some other spells, and these spells are possible to use in a surprise segment.”

 

PHB, p. 105: “[During the Surprise segment] the thief darts to the rear of the party to attempt to hide in the shadows and attack from behind when opportunity presents itself”.

During Round 1, the thief is “successfully slinking and sliding around in the shadows [past 20 orcs and the illusionist 30′ away, to end up behind the illusionist]”. And Round 2 the thief stabs the illusionist from behind with his sword!

So our thief managed to somehow move behind everyone while Hiding in Shadows. Yet it’s not possible to move while the area is under observation (say, by 20 orcs and an illusionist):

PHB, p. 27: “Hiding in shadows is the ability to blend into dark areas, to flatten oneself, and by remaining motionless when in sight, to remain unobserved.”
DMG, p. 19: “this is NEVER possible under direct (or even indirect) observation. If the thief insists on trying, allow the attempt and throw dice, but don’t bother to read them, as the fool is as obvious as a cool pile in a ballroom. If a hidden thief attempts movement while under observation, the proverbial jig is up for him or her.”

 

DMG, p. 20: “Therefore, if an 8th level assassin snuck up on and surprised a 10th level magic-user in the dungeon and successfully assassinated him, the assassin would receive 1,000 x.p. plus another 100 x.p. since the magic-user was 2 levels higher than he. However, since it was a simple mission, the total 1100 x.p. would be multiplied by 1/2, giving 550 points. This is added to the 2400 x.p. normally received for killing this magic-user, making a final total of 2950 x.p.  earned, exclusive of fees.”

The implication here is that an assassin sneaks up and surprises while on a “simple mission”. Yet assassination comes in two forms, the planned assassination (“missions”) and that which occurs during a standard encounter. PHB, p. 29: “Assassins attack on the same combat tables as thieves do, including back stabbing. However, if they surprise (q.v.) a victim, they may attack on the ASSASSINATION TABLE. … The assassin decides which attack mode he or she will use: assassination, back stabbing, or normal melee combat.”  With surprise during a standard encounter, assassins can use the assassination table if they have surprise.  For a planned assassination, DMG, p. 75: “If the assassination is being attempted by or in behalf of a player character a complete plan of how the deed is to be done should be prepared by the player involved…” and DMG, p. 20: “The explanations for difficulty given under SPYING should be used as guidelines”.

That’s fairly clear. For normal attacking, assassins can use the ASSASSINATION TABLE. The DMG reference on p. 20 is simply clarifying that, combat counts as a “simple” assassination for purposes of calculating XP. Assassination missions are similar to spying missions.

 

DMG, p. 41: For each such additional hit die, the skeleton or zombie will gain another die. Thus, the animated skeleton of a fire giant, an 11 hit die monster, is 10 over the norm for a skeleton normally animated, so it would have 1 + 10 hit dice (11d8). Likewise, a fire giant zombie would have 10 dice over and above the sort of creature typically made into a zombie, so it would have 2 + 10 hit dice (12d8).

A fire giant skeleton would have 11d8 hp? Yet in MM2, an animated giant skeleton (created by the 5th level Animate Monster spell) would have 6d8 hp. This is at least reasonably clearly that a fire giant skeleton created with Animate Dead would have d8 + 10 hit points (at least in the context of the later MM2). Otherwise the 3rd level Animate Dead spell is far more powerful.

 

DMG, p. 71: “Balto attacks Aggro (who is in AC 2) with his staff. He needs a base 18 to hit, and the -7 armor class adjustment for sword vs. plate mail and shield makes this a 20.”

The DMG errata clarifies this is a staff, so it’s the AC adjustment that is wrong.

 

DMG, p. 71: “First, Arlanni the thief, who had her sling ready (as the player had stated previous to the encounter), fires a shot at Blastum, who is obviously a magic-user.”

In this case, Party A (which includes Arlanni) has two segments of surprise. While the PHB permits only 1 arrow / segment of Surprise (“Physical attacks during surprise situations are also possible on o 1 per segment basis, whether the form is by weapon, projectile, or method intrinsic to the creature”), the DMG changed that to: “Even if distance prevents striking with weapons, the discharge of arrows, bolts or hand-hurled weapons is permissible at three times the normal rate providing the weapon/missiles are ready, otherwise at normal rates for rounds.”

 

 

DMG, p. 71: “Meanwhile, Blastum has been preparing a shocking grasp spell, and now he steps forward and touches (rolls a successful “to hit” die score) Arlanni the thief…

Blastum casts a spell, and then moves? PCs can’t cast spells and move. They can’t move before casting as spell either (with the exception being flying). One must conclude that the “steps forward” is flavor text as the two parties are “only 10′ apart” and Arlanni is considered in reach.

 

DMG, p. 71: “Meanwhile, Blastum has been preparing a shocking grasp spell, and now he steps forward and touches (rolls a successful “to hit” die score) Arlanni the thief, delivering 10 points of damage (1-8 + 4). There is no saving throw: Arlanni has only 8 hit points, and dies. … On the left, Aggro again attacks Balto with his axe. He rolls a 12 and hits him for 5 points. Balto only had two points left, so he is dead.”

But do Arlanni and Balto die at -2 and -3 hit points respectively? When exactly do PCs die? We know from DMG p. 82:

“When any creature is brought to 0 hit points (optionally as low as -3 hit points if from the same blow which brought the total to 0), it is unconscious. In each of the next succeeding rounds 1 additional (negative) point will be lost until -10 is reached and the creature dies.”

There are a number of ways to parse this whole thing incorrectly, making the example even more confusing. PCs go unconscious when at—or below—0 hit points (optionally not falling unconscious until -3 hit points), and die at –10 hit points. DSG supports that: “When a character’s hit point total reaches -10, he is dead.”

 

DMG, p. 97: “A large spider has surprised her [the MU]. As she went to examine the refuse it dropped from its web. It landed on her back and bit her. Before you can take any action, she must make a saving throw with t 2 on her die, of course, and then she and the spider must dice for initiative and fight a round of combat. After that the rest can try to do something.”

Why exactly would the MU be rolling for initiative when the rest of the party is not? There’s surprise, and then party initiative.

 

DMG, p. 98: “(Rolling a d6 behind a screen so that the players cannot see the result which would normally indicate if noise were detected or not, if applicable, when a character listens. In this case the DM knows what will be heard, but pretends otherwise.)”

There’s no indication anywhere else that a d6 is rolled for hear noise. When listening at a door (DMG, p. 60), a d20 is rolled.

 

The Dimwall encumbrance example in the DMG (Appendix O, p. 225) suggests the capacity of a backpack as at least 400:

  • hand axe: 50
  • 3 flasks of oil: 20 × 3
  • a candle: 5
  • 3 small sacks: 5 × 3
  • 1 large sack: 20
  • 7 torches: 25 × 7
  • 50′ Rope (lashed): 75

Total: 400

And his companion Druge:

  • 10 spikes: 10 × 10
  • 1 week’s iron rations: 75
  • flask of oil: 20
  • 50′ rope (strapped): 75
  • heavy crossbow (hanging from pack): 80

Total: 350

Now both examples include rope “lashed in a bundle” but lashing stuff to the pack as far as I’m concerned is a standard pack thing. If you don’t count the rope, Dimwall’s backpack capacity is 325. Yet the AD&D Character Sheets list the capacity of a backpack as 3 cu. ft (300 gp).

While the weight of a standard spell book is 150 gp, “The encumbrance value of a spell book equal to three times its weight (450 gp or thereabouts), although it is correct to assume that a volume will fit within an otherwise empty backpack or large sack.” (UA, p.  79). It makes more sense to assume it’s just barely squeezing into a pack with a 400 capacity than a pack of 300! 400 is consistent with the earlier value of 400 cn in Set 1: Basic. The Character Sheets are wrong.

 

Depending on your edition of the DMG, the extended combat example on p. 71 has numerous errors. They’re updated in the errata for the DMG and later printings of the DMG, so I won’t detail them further here.

 

Anything else?

References

Players Manual: Set 1: Basic Rules, 1974.
TSR 2010, Players Handbook [1e], 1978.
TSR 2011, Dungeon Masters Guide [1e], 1979.
TSR 9028, Player Character Record Sheets, 1984.
TSR 2017, Unearthed Arcana, 1985.
Dragon Magazine Issue 124, Packing It All Away, August, 1987, p. 54.

Back Stab By The Numbers

Last Updated: 220204 … 220611 (heavily revised)

Back stabbing is the striking of a blow from behind, be it with club, dagger, or sword. The damage done per hit is twice normal for the weapon used per four experience levels of the thief, i.e. double damage at levels 1-4, triple at 5-8, quadruple at levels 9-12, and quintuple at levels 13-16. Note that striking by surprise from behind also increases the hit probability by 20% (+4 on the thief’s “to hit” die roll).

There’s a lot of uncertainty and misunderstanding about the relative “power” of back stab.  As the thief’s abilities often boil down to back stab, many DMs limit thief abilities. So just how good is back stab, really?

Let’s perform a reasonably direct comparison to the fighter:

  • A fighter, 0 XP, Level 1, Strength 17, THAC0 20 –1 (Str), armed with a long sword (average 4.5 points of damage +1 (Str))
  • A thief, 0 XP, Level 1, Dexterity 17, THAC0 20–4 (back stab), armed with a longsword (average 4.5 points of damage × 2 (back stab)) ). MS: 15%+5% (Dex), HiS: 20% + 5% (Dex).
  • Our generic monster, AC: 5.

Both have a 17 in their Prime ability (Dexterity and Strength respectively), increasing the fighter’s To Hit and Damage, and the thief’s chance to MS and HiS. The thief’s backstab, on average, decreases an opponent’s AC by 1 (no Dex or shield bonus).

In a discussion of THAC0, you have to consider the early repeating 20 in the thief’s to hit chart, and adjust appropriately. A further consideration when comparing classes is relative level for commensurate XP. Generally, a thief should be one level higher than a fighter starting at level 3:

THAC0

Level 1 2 3 4 5 6 7 8 9 10 11 12
Fighter 19 19 17 17 15 15 13 13 11 11 9 9
Thief (+4)* 15 15 15 15 13 13 13 13 10 10 10 10
T (+4,lvl adjusted)* 15 15 15 13 13 13 13 11 11 11 11 9
* Adjusted for the thief’s 20,20,19 … in the THAC0 chart, Str bonus, Dex benefit lost.

At low levels, the +4 bonus to hit makes a thief more likely to hit than the fighter, but the fighter’s more rapid THAC0 advance overwhelms the +4 bonus by level 7.

Number of Attacks

While the fighter attacks (at least) every round, back stab is limited in frequency. For the thief to back stab, they must approach, back stab, then retreat in order for their opponent to be no longer aware of their presence. Assuming that takes but 2 rounds:

Attacks / Level 1 2 3 4 5 6 7 8 9 10 11 12
Fighter 1 1 1 1 1 1 3/2 3/2 3/2 3/2 3/2 3/2
Thief .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5 .5

Damage

The thief gains a damage multiplier on back stab, but fewer attacks/round. If we assume both the fighter and thief are using a long sword (average 4.5 hp of damage), then for each hit our fighter does 5.5 hp damage, where the thief using back stab will average 9 damage (levels 1-4), 13.5 damage (levels 5-8), or 18 (levels 9-12).

Putting the Pieces Together

Now, considering our “average” AC:5 monster, that brings us to a simplistic chance to hit per attack of:

Chance to hit AC: 5 1 2 3 4 5 6 7 8 9 10 11 12
Fighter (Str +1) 35% 35% 45%* 45%* 55%* 55%* 65%* 65%* 75%* 75%* 85%* 85%*
T (lvl adj. +4 back) 70% 70% 70% 80% 80% 80% 80% 90% 90% 90% 90% 100%

* Ignoring that our fighter will almost certainly specialize. And again…

Given our fighter also has +1 to damage from strength, the average damage per attack is:

Damage/attack 1 2 3 4 5 6 7 8 9 10 11 12
Fighter (Str +1) 1.9 1.9 2.5 2.5 3.0 3.0 3.6 3.6 4.1 4.1 4.7 4.7
Thief (lvl. adj w/ mult) 6.3 6.3 6.3 7.2 10.8 10.8 10.8 12.2 16.2 16.2 16.2 18.0
Damage ratio/attack 3.3 3.3 2.5 2.9 3.6 3.6 3.0 3.4 3.9 3.9 3.5 3.9

Or, put another way, the thief’s back stab averages 3.4 times the damage of a fighter hit-for-hit. Not bad! However, while the thief can only (best case) back stab once every two rounds, the fighter’s attacks per round increase, and the thief’s relative chance to hit decreases. A more accurate ratio looks more like:

Damage/round 1 2 3 4 5 6 7 8 9 10 11 12
Fighter (Str +1) 1.9 1.9 2.5 2.5 3.0 3.0 3.6 3.6 4.1 4.1 4.7 4.7
T (lvl. adj) 3.2 3.2 3.2 3.6 5.4 5.4 5.4 6.1 8.1 8.1 8.1 9.0
Damage/round 1.6 1.6 1.3 1.5 1.8 1.8 1.5 1.7 2.0 2.0 1.7 1.9

Using back stab most generously (every other round), the thief averages 1.7 times damage as a fighter. Nothing earth-shattering—if the thief can back stab every other round, he’s in the ball park of a fighter, but far more vulnerable (AC, HP) once engaged in melee. Hopefully their opponent lets them withdraw. Otherwise the thief remains locked in combat after the initial back stab attempt, with his worse hit points, THAC0 and armor class—not ideal.  Or flee, providing their opponent a +4 bonus in return!

The GM likely requires the thief to move around to their opponent’s back again, for an additional round for the opponent to “lose awareness” (assuming their opponent doesn’t pursue!), bringing that ratio down to 1.1 times the fighter.

Skill Checks

The Level 1 fighter requires a 14 To Hit, so: 35% (TH) * 5.5 Damage (Str) = 1.9 DPR.

Assume the best case: back stab every other round, and no other checks:

Our Level 1 thief requires an 10 To Hit, and: (45% (TH) * 9 Damage (Back stab) ) = 2 DPR.

In other words, back stab DPR looks awesome—better than the fighter! Back stab includes one more consideration—thief abilities. Move Silently is used “to approach to back stab”. Failure means that movement was not silent, and thus back stab fails. The ability to move silently ranges from 10% to 99%, but even a 9th level thief will only succeed 70% (barring race and Dexterity modifiers). That brings our thief back stab / two round damage number down to 50% of the fighter:

Damage/round w/ MS 1 2 3 4 5 6 7 8 9 10 11 12
Fighter (Str +1) 1.9 1.9 2.5 2.5 3.0 3.0 3.6 3.6 4.1 4.1 4.7 4.7
Thief (lvl. adj) 1.1 1.6 1.6 1.8 2.7 2.7 2.7 3.0 4.1 4.1 4.1 4.5
Move Silently (level adj) 0.2 0.3 0.3 0.4 0.5 0.6 0.6 0.7 0.8 0.9 0.9 1.0
Damage ratio/round 0.1 0.2 0.2 0.3 0.4 0.5 0.5 0.6 0.8 0.8 0.8 1.0

(For other comparisons, the chance to Hide in Shadows is worse than Move Silently)

In other words, a lot of math later, on a round-by-round basis, the thief, using his premium back stab ability, with back stab every other round, averages 50% of the damage of a fighter. To back stab, he further exposes his poorer AC and hit points to attack. Under the assumption he’s using a long sword, instead of the perhaps more frequent club or dagger.

Multiple Skill Checks:

Some GMs require MS and HiS rolls instead of, or in addition to Surprise. If the GM requires MS (or HiS depending on the GM), we get to the meat of the issue:

Fighter melee DPR (d8) 1.9
Thief back stab DPR 2.03
Thief back stab DPR w/ MS 0.41
Thief back stab DPR w/ HiS 0.30
Thief back stab DPR w/ MS × 2 0.08
Thief back stab DPR w/ His + MS 0.06

With only a single MS check, the fighter averages 429% more damage. Should the GM require two successive checks, the thief’s back stab DPR drops through the floor—the fighter averages 20× more damage than a thief with back stab! If you ask yourself, “Why do my thieves never back stab?”, this would be why.

Surprise

By the Book, Surprise—not MS, not HiS—is required for back stab. Let’s evaluate the thief’s back stab DPR with Surprise. The default chance for Surprise is 2 in 6. A silent thief increases that range to 3 in 6. A silent hidden thief increases that Surprise range to 4 in 6.

“Assume the party of characters, moving silently and invisibly, comes upon a monster. They have 4 of 6 chances to surprise.” PHB, p. 103.

With a generous GM, a thief approaching from behind could be considered invisible (at least hard to see since the thief is by definition at their opponent’s back), receiving the benefit of being hidden after a successful MS.

The Level 1 thief’s back stab DPR under Surprise:

Thief Back stab DPR w/ Surprise (2 in 6) + To Hit 0.60a
Thief Back stab DPR w/ Surprise (w/ MS bonus) (3 in 6) + To Hit 0.76a
Thief Back stab DPR w/ Surprise (w/ MS bonus + auto Hide from rear) (4 in 6) + To Hit 1.07a

aSurprise includes a 16% chance for one attack, a 16% chance for two additional attacks, and (potentially) chances for 3 or even 4 attacks depending on the modified Surprise roll.  Additional back stabs don’t multiply damage, and are only +2 to hit—see Polyhedron #31, p. 29.

If the L1 thief rolls Surprise for a successful back stab, their DPR is .6. If you incorporate a MS check before the Surprise roll to increases the chance of Surprise to 3 in 6, the DPR increases. If you assume that MS includes being hidden (hard to see someone approaching successfully from behind), then their DPR is better yet. Our thief’s DPR is less than that of the fighter, but using Surprise is better than a single MS check.

And the same comparison with our PCs leveled up to the thief’s triple damage? One can quibble about the thief’s speed of advancement for levels, but the levels for the two classes still overlap in this range, so any difference between the two classes is brief.

A thief, 19,000 xp, Level 5, Dexterity 17, THAC0 19 – 4 (back stab). MS: 40%+5% (Dex), HiS: 31% + 5%(Dex), armed with a longsword (average 4.5 points of damage × 3 (Back stab))

A fighter, 19,000 XP,  Level  5, Strength 17, THAC0 16 –1 (Str), armed with a long sword (average 4.5 points of damage +1 (Str))

Here’s all the data in totality:

Prime: 17, Long sword, Opponent AC:5 Level 1 Level 5
Fighter Melee DPR 1.93 3.03
Thief Melee DPR 1.13 1.58
Thief Back stab DPR (only To Hit, no other mods) 2.03 3.71
Thief Back stab DPR w/ MS + To Hit 0.41 1.67
Thief Back stab DPR w/ HiS + To Hit 0.30 1.34
Thief Back stab DPR w/ MS + MS + To Hit 0.08 0.75
Thief Back stab DPR w/ His + MS + To Hit 0.06 0.60
Thief Back stab DPR w/ Surprise (2 in 6) + To Hit 0.60 0.96
Thief Back stab DPR w/ Surprise (w/ MS bonus) (3 in 6)  + To Hit 0.76 1.41
Thief Back stab DPR w/ Surprise (w/ MS bonus+auto Hide from rear) (4 in 6) + To Hit 1.07 2.32

 

Other considerations should you desire more math:

  • A 1e fighter likely has additional bonuses to hit beyond a base 17 Strength. If the campaign uses Specialization, the fighter will have additional bonuses to hit in addition to additional attacks / round.
  • At L6 the fighter’s attacks go to 3/2 without specialization (or 2/1 with specialization), increasing DPR by 50%.
  • If the GM limits the thief to only one back stab every three rounds, all of the thief DPRs decrease 33%.
  • If the attack renders a creature dead, who cares if you compare a back stab 10 hp / round vs 4 hp / round when the creature has only 4 hp?
  • A good argument can be made that Surprise can, at most, provide only 2 additional attacks, as defined as “Surprise” (1 segment) and “Complete Surprise” (2 segments), where the above assumes the possibility of up to 4 segments of Surprise.

The net result is that calculating back stab damage by Surprise has a higher DPR for the thief, yet still considerably less than a fighter of comparable level. Calculating back stab taking more than two rounds, or requiring multiple rolls for success, almost guarantees futility for the thief and back stab.

 

And of course, back stab isn’t always an option. Certain creatures (otyughs, slimes, molds, etc.) either negate surprise or have no definable “back”, thus negating this ability. Back stab isn’t possible against those “aware” of the thief. Depending on the GM, the opponent could be deemed aware after the first attack, so only once per melee. Results swing further when you start to include a more usual fighter to hit/damage bonus from Strength.

UA further lessened back stab with weapon specialization providing fighters a 50% increase in number of attacks (and thus a 50% increase in damage), an increased chance to hit, and a ≥ 20% increase in damage (with at least +1 damage from weapon specialization). And that’s ignoring specializing more than once.

Recommendations

Don’t, just don’t, require multiple skill checks.  Use Surprise, improved by MS (or HiS).

Don’t fear the thief getting to back stab more than once in a fight. The time he spends moving around limits the overall damage per round.

While +4 to hit looks good, over levels it loses value in comparison to the fighter’s THAC0 table. The thief’s bonus to hit should increase at the same rate as the damage multiplier. While you could permit a thief to specialize, that’s not quite the advantage it appears given the thief’s fewer proficiency slots. A flat additional +1 to hit at level 5-8, +2 to hit at levels 9-12 makes back stab scale better, especially if playing with weapon specialization.

While back stab has the occasional wild swing (rolling max damage with a 4× multiplier), the reverse is also true when the high-level thief rolls a “1” for 4 points of damage. Back stab is hard to pull off, and exposes the thief to significantly more peril. If the back stab is successful, a minimum of damage would help offset the risk—a 2-point minimum at level 5, a 3-point minimum at level 9, etc.