Last Updated: 240219
magicresistant@corwyn.net
Well, my players are now regularly both interacting with magic-resistant creatures, and high enough level to start creating complicated questions. Let’s put all the pieces together in one place.
Typically you can look across the different AD&D books to gain rule insights. Magic resistance is surprisingly resistant to that. Across the Monster Manual, Dungeon Masters Guide, Fiend Folio, and Deities & Demigods, the text is virtually identical with the additional sentence here or there. Consolidating that text:
Magic resistance indicates the percentage chance of any spell absolutely failing to affect the magic-resistant creature. It is based on the spell being cast by a magic-user of 11th level, and it must be adjusted upwards by 5% for each level below 11th or downwards for each level above 11th of the magic-user casting the spell. Thus a magic resistance of 95% means that a 10th level magic-user has no possibility of affecting the monster with a spell, while a 12th level magic-user has a 10% chance.
Even if a spell does take effect on a magic-resistant creature, the creature is entitled to normal saving throws. A creature’s magic resistance extends only to its immediate possessions, i.e., anything carried or worn. Area-affect spells will still function if targeted with a magic-resistance creature within their area; the creature itself might not be affected, though all others in the spell area will be subject to spell effects (A fireball, for example, may wipe out a cluster of orcs, and a devil standing in their midst might be totally unaffected due to its magic resistance). Note also that the magic resistance of a creature has an effect on certain existing spells such as hold portal, where it indicates the probability of the magic resistance shattering the existing spell.
Only spells and spell-like abilities and effects (including those cast from an item1, and potions1) from creatures and magical devices are subject to magic resistance. The level of magic-use can be determined for certain items; wands operate at 6th level, staves at 8th level, rings at 12th level, potions at 7th, etc. Spells cast from items with no level of magic use are assumed to be12th level unless a higher level would be required to cast the spell. Breath weapons, gaze weapons, special attacks (such as disease, turn undead, energy drain, or paralysis), magical weapon bonuses and their special abilities (like vorpal), illusions, and psionics are not. The spell effects on the surroundings are not negated by a successful resistance roll (a lightning bolt can still destroy the bridge a balrog is standing on). If a resistance roll succeeds against a magical wall, the magic-resistant creature can walk through2.
Evocations spells are almost always subject to magic resistance if inflicting damage. Alteration spells are subject to magic resistance if they transform the target creature, but not if they are targeted on a point in space instead (e.g., Transmute rock to mud and wizard eye change a creature’s surroundings, not the creature itself, and thus not subject to magic resistance). Spells that conjure/summon creatures are never subject to magic resistance. Necromancy spells that alter the target creature’s life force are subject to magic resistance.2 Illusions spells are almost never subject to magic resistance except those inflicting a direct attack, such as phantasmal killer or blindness. Magic resistance does not allow a creature to disregard illusions, see beings who are hidden magically, or otherwise allow the creature to have any control over existing magical influences, spells, or powers that only affect other creatures.
Hold portal can be shattered if preventing a magic-resistant creature from opening a door. There are certain spells, however, that if cast upon an area may not be triggered by the passage or touch of a magic resistant creature. Magic mouths, symbols, glyphs of warding, and fire traps will not be activated if the creature makes its MR roll, but will still be present and may be activated later. 1
Magic-resistant creatures have a measure of control over their ability. A creature can voluntarily nullify its magic resistance in order to take advantage of the effects of a beneficial item, spell or spell effect. Nullifying one’s own magic resistance requires total concentration (no other physical or mental activity), and must be performed during the round in which the casting of the spell or spell-like power takes effect. The target creature does not need to maintain concentration on negating its magic resistance after the magic gets a foothold (the spell effect is now included with the recipient, and the magic will run its course). During the round (or longer) that a magic-resistant creature maintains concentration on negating its resistance, it is completely vulnerable to any magical effects (not necessarily beneficial) directed toward it. Not even a saving throw is allowed, since any saving throw against any form of magic is essentially just another form of magic resistance.1
Magic-resistant creature can use and benefit from the wearing or carrying of magic items. A creature attempting to put on and make use of a cloak of displacement or girdle of giant strength, for instance, must simply lower their magic resistance and touch the item or make a normal magic resistance roll. If the creature’s magic resistance fails (on this check), the item can be donned and worn, with all of its effects occurring to the wearer as if that creature had no magic resistance.1 In the case of dwarven and halfling 20% resistance to magic rings, they must recheck each time they put on the ring.
Bibliography
TSR 2010, Players Handbook, 1978.
TSR 2011, Dungeon Masters Guide, 1979.
1Dragon Magazine Issue 79, Magic Resistance: What it is, how it works, 1983.
TSR 2017, Unearthed Arcana, 1985.
2Dragon Magazine Issue 218, Magic Resistance, Step by Step, June 1995. [2e]
