The higher a being's MR, the less likely that it will be affected by an enchantment cast on it. Beings that are magical in some way (such as elves or sirens), magic-users, and those that are non-natural tend to have higher MR than other creatures.
Monster MR is partly based on hit dice, so monsters with high hit dice tend to be highly resistant to magic. Most monsters with one hit die have a 50% chance to fail to resist outright, in addition to the normal saving throw. Finally, some monsters are outright immune to magical enchantments - for instance, most nonliving creatures.
Some of these effects can come from potions, weapon brands, clouds, or spells that are not considered enchantments.
- Banshee card
- Blink Other (but not Blink Other Close)
- Brain Feed
- Cause Fear
- Control Undead
- Crusade card
- Damnation card
- Dimension Anchor
- Dispersal spell (only teleportation, blink away cannot be resisted)
- Enslave Soul
- Ensorcelled Hibernation
- Inner Flame
- Mass Confusion
- Metabolic Englaciation
- Scroll of fear
- Sentinel's Mark
- Strip Resistance (ignores its target MR 1 of every 3 times)
- Teleport Other
- Wand of confusion
- Wand of disintegration
- Wand of enslavement
- Wand of paralysis
- Wand of polymorph
- Wand of slowing
- Wand of teleportation
MR does not prevent effects triggered through the spell Alistair's Intoxication.
- Many of these enchantments can be resisted via other means. For instance, life protection counters the effects of Agony (but not the Pain spell). Undead, nonliving, and plant monsters cannot sleep.
- Polymorph will not be resisted by (very) ugly things, which will always change color. Shapeshifters can only resist it if they are currently in the form of something immune to magic.
- Effects produced by the chaos brand don't check MR.
Resisting an enchantment is dependent on the resisting creature's MR and the enchantment power (which is a function of the spell power) of the enchantment it is resisting. The formula is:
If 1d100 + 1d101 is less than 102 + MR - the enchantment's power, the enchantment is resisted.
This is sometimes referred to as a "saving throw", after the die-based resistance system employed in Dungeons & Dragons.
Enchantment power is your spell's power multiplied by a modifier (usually 1) and then passed through a stepdown function which halves your spell power every 30 points above 40. Agony, Pain, Slow, Corona, Teleport Other and all the mass enchantments have modifiers greater than 1. Ensorcelled Hibernation has an additional stepdown.
Neither the player's nor monster's MR is ever given explicitly, but a rough suggestion of how magic resistant they are can be seen by pressing the @ or % key for the player, and examining a monster's description.
Magic resistance adjectives are as follows:
|MR description||% screen||MR number|
As a practical matter, a player who is "incredibly resistant" should be able to usually resist the most dangerous enchanters in the game (such as Kirke, deep elf demonologists, and even ancient liches). More MR will reduce the likelihood of these spells landing even further, but the gains become significantly less important beyond this point.
Player resistance is determined as below:
Experience level × racial multiplier, plus the following:
- Shadow Form: Immune
- Randart MR (40 for each +)
- 40 for each armor of magic resistance
- 40 for each ring of protection from magic
- Ranks of the MR mutation × 40
- 50 when lichform
- 70 when using Trog's Hand
- Everything is then divided by two if the player is under the effect of a scroll of vulnerability, the attack of a phantasmal warrior, or the Strip Resistance spell.
Racial multipliers are as follows:
- 7: Spriggan
- 6: Purple draconian, deep dwarf, felid
- 5: Naga, mummy, vine stalker
- 4: High elves, deep elves, demigod, vampire, formicid, ogre
- 3: Humans and every other race
Prior to 0.14, when a target resisted a spell, the message would indicate how poorly they fared on that particular resistance roll instead of how difficult in general it is for the target to resist the spell.