Last Updated: 181118
I abandoned using Surprise years ago—so long ago I don’t specifically remember why. I suspect because I tried to make the rules make sense, and as written they don’t (and can’t, there are errors in the early printings of the PHB and DMG!). The rules are also surprisingly (hah!) unclear on who rolls for what effect. Am I rolling for whether I’m surprising or surprised? What if the result is modified more than once?
I’ve recently been inspired to dig into some of the more fiddly AD&D rules, and have been impressed at how well those rules work once I understand them, so I thought I’d try Surprise again. That said, I’ve modified the below just a bit to be consistent with the rest of my house rules (see Initiative). I also limit surprise to a single attack per segment, without stacking, to a maximum of 2 segments. That’s intentional, otherwise 7th level Elven Ranger catching someone completely flat-footed could gain 10 melee attacks during surprise (and more extreme examples exist!)
A surprised party is one caught unawares or unprepared. In such circumstances the non-surprised (or less surprised) party has an advantage reflected in up to [n] segments of actions against the surprised party prior to initiative (where I choose to limit [n ]≤2). It is possible for both parties to be surprised equally—with surprise thus having no effect.
Prior detection negates the possibility of surprise. Light can spoil the possibility of surprise. Noise can negate surprise considerations, whether the sound is the normal progress of the party or the effect of a fruitless attempt to open a door. Magical devices can possibly negate surprise by detection of thoughts or intentions. In all such cases, only parties subject to surprise roll for surprise (DMG, p.62).
Assassins can don disguise to create the opportunity for surprise. There is only a 2% chance per day that the victim (or one of their henchmen) will notice the disguise. A combined total Wisdom and Intelligence above 20 increase that chance by 1% per point (PHB, p.29).
If either or both parties are surprised, the distance will typically be 1″ to 3″, as surprise is normally a factor only in close encounter situations. When outdoors or otherwise appropriate for ranged encounters, the distance (6d4”)is reduced by reduced (or increased) by 1” for each segment of surprise (DMG, p. 49).
For each side, if the chance of surprise exists, they roll d6 once to determine whether their side is surprised. By default, on 1 or 2 their side is surprised for 1 or 2 segments, otherwise they are not surprised. “Surprise” indicates 1 segment of surprise; “Complete Surprise” is defined as 2 segments of surprise [c.f. , DMG, Crossbow of Speed], OR as 4 segments of surprise (c.f., PHB, Aerial Servant spell). Note I use a maximum of 2.
Modifiers to the Chance of Being Surprised (Your Die)
A party is surprised only as easily as its most perceptive member if that awareness can be communicated; in a party with a ranger (surprised only on 1 in 6), the entire party is only surprised on a 1. If awareness is limited (such as a human ranger in the dark), special class or race benefits do not apply (WSG, p. 60).
- Rangers (& Duelists) are surprised only on 1 in 6 (decreasing the range by 1, normally to 1 in d6 instead of 1-2 in d6) due to their alertness.
- Barbarians are surprised only on 1 in 10 (decreasing the normal range by 4 from 2 in d6 to 1 in d10 (see Calculating Cumulative Surprise below) due to their alertness. This further decreases the normal range by an additional 2 (to 1 in 20) if in familiar terrain.
- The monk’s chance of being surprised drops 2% per level, thus a 5th level monk reduces the range to be surprised by 1 (only 1 in 6) due to their alertness.
- With a proficiency check, characters with Alertness are surprised only on 1 in d6 (decreasing the range by 1, normally to 1 in d6 instead of 1-2 in d6). This does not stack with other class abilities–those classes effectively have this proficiency without a requirement for a proficiency check.
- The Dexterity Reaction/Attacking Bonus affects that many segments of surprise for that individual only and only if carrying “light gear” [Unless not encumbered], e.g. on a range of 1-2, with the group rolling a 2, a character with a 16 Dexterity (+1 Reaction/Attacking) would be surprised for only 1 segment. If an opponent attempts to attack them during a Surprise segment, the attack is deferred to the standard initiative round (DMG, p. 62).
Modifiers to the Chance of Surprising Others (Their Die)
A party with an increased chance to surprise their opponents increases their opponents’ range from 1-2 on d6 to 1-3 or more (also increasing the potential number of segments that their opponent(s) can be surprised), but only if that increased chance of surprise is true for the entire party (e.g., all rangers, a group of only halflings and elves 90’ in advance not wearing armor, all huge spiders, etc.).
- Hiding in Shadows increases the opponents’ chance of being surprised by 1 (increasing the opponents range by 1, e.g. surprised on 1-3 in d6 instead of 1-2 in d6) due to being hidden.
- Invisibility increases the opponents’ chance of being surprised by 1 (increasing the opponents’ range by 1, e.g. surprised on 1-3 in d6 instead of 1-2 in d6) due to being hidden.
- Move Silently increases the opponents’ chance of being surprised by 1 (increasing the opponents’ range by 1, e.g. surprised on 1-3 in d6 instead of 1-2 in d6) due to stealth.
- Elves and Halflings surprise opponents 1-4 in d6 when not in metal armor and 90’ in advance (increasing their opponents’ range by 2, e.g. surprised on 1-4 in d6 instead of 1-2 in d6), due to their ability to be hidden and move stealthily. If they have opened a portal, that chance for surprise returns to 1-2 in d6.
- Rangers surprise opponents 50% of the time (increasing their opponent’s chance of being surprised by 1, e.g. surprised on 1-3 in d6 instead of 1-2 in d6) due to their stealth. This definition doesn’t include conditions to surprise, but rangers can’t surprise opponents aware of their companions and thus includes same range requirement as elves and halflings that rangers must be at least 90’ in advance. Armor however is not a factor.
- Barbarians increase their opponents’ chance of being surprised by 1 (increasing the opponents range by 1, e.g. surprised on 1-3 in d6 instead of 1-2 in d6) due to being hidden, with an additional 1-point increase if also familiar terrain (e.g. surprised on 1-4 in d6 instead of 1-2 in d6), due to their ability to hide in known terrain). Again, this definition doesn’t include condition to surprise, but barbarians can’t surprise opponents aware of their companions and thus includes same range requirement as elves and halflings that rangers must be at least 90’ in advance. Armor however is not a factor.
Modifiers are cumulative when dissimilar. Example: A lone invisible elf not wearing metal armor comes upon an orc. The standard chance of being surprised is 1-2 in d6. For the orc, its range is increased due to the elf (+2), but not further increased due to the elf’s invisibility (+1); the orc will be surprised if it rolls 1-4 on d6. The elf rolls a 2, and the orc rolls a 4. The Elf is surprised for 2 segments, the orc for 4. For the first two segments they stare at each other, after which time the elf has 2 segments (the maximum) to act before beginning standard initiative.
In the example above, if the elf had a Dexterity of 17 and was only lightly encumbered, the elf would reduce the number of rounds it was surprised by 2, and (except that I limit the number of actions to 2) would have 4 segments to act.
For any segment that both parties are surprised, nothing happens. While the attackers’ opponent(s) is/are surprised, but the attacker is not, the attacker may:
- Do nothing, or attempt to parlay.
- Move 1” (and potentially close for melee).
- Prepare (i.e., drawing or setting a weapon).
- Charge up to 1” and execute one attack (melee, or grapple), if prepared and ready.
- Melee or grapple (if prepared and within 1”)
- Fire a missile weapon, if prepared and ready.
- Use a breath weapon (if normally possible!).
- Attempt to activate a magical device. If not enough surprise segments exist to complete activation, apply time towards initiative roll as -2 per surprise segment (which means the device could activate during surprise).
- Roll on the Assassination Table (if an assassin).
- Strike from the rear with damage multiplier for back stab (if thief or assassin and, of course, from behind) at +4 to hit instead of the standard rear attack bonus of +2. Striking from the rear also negates any shield or dexterity bonus. After surprise ends, if a thief removes themself from melee such that their opponents are no longer aware of the thief’s presence, the thief could reenter combat, attempt to move silently behind their opponent, and back stab. However, they can’t gain surprise, so have only the standard rear attack.
- 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. Other, longer casting time spells can only be begun during surprise (DMG, p. 61), and if not completed subtracting 2 for each surprise segment from future initiative rolls.
- A party successfully listening at a door negates the possibility of surprise if they hear something.
- An attack when using Dust of Disappearance is always by surprise (assuming for the entire party). Roll normal surprise, with a minimum of 1 segment of surprise for the opponent.
- A character wearing the Robe of Eyes cannot be surprised.
- The Crossbow of Speed can fire on the 2nd segment of complete surprise.
- Sandstorms and frostbite both increase the chance to be surprised by 1 (increasing the party’s potential range by 1).
- A garrote attack will only succeed with surprise from behind.
Calculating Cumulative Surprise (Optional)
Any time the range of surprise for a group would be reduced to 0 (e.g. a 0 in 6 chance), the die size is incremented instead (next 1 in 8, then 1 in 10, etc.). A party where everyone was unencumbered with a Dexterity of 17 (a +2 Reaction Adjustment) would therefore be surprised on 1 in 8. If the group also had a ranger, the chance of surprise would be 1 in 10.
There are rare instances where surprise could be converted into d100. If the opponent uses a different die than d6 to calculate surprise (d8, d10, even d20), then modifications to their range of being surprised could be calculated on d100 (such as adding 16.67% from the ranger ability to the 5% chance of the creature surprised only 1 in 20). Instead, modify by the same number (applying the “1” from the 1 in 6 chance to the 1 in 20, making the range 2 in 20), because that’s faster, easier, and reflects the increased difficulty to surprise that creature.