Spell resistance (abbreviated SR) is the extraordinary ability to avoid being affected by spells. Some spells also grant spell resistance.
To affect a creature that has spell resistance, a spellcaster must make a Caster Check with a result that is greater than or equal to the creature's spell resistance. The defender's spell resistance is like an Armor Class against magical attacks. If the caster fails the check, the spell is wasted, having no effect on the target creature. The possessor does not have to do anything special to use spell resistance. The creature need not even be aware of the threat for its spell resistance to operate.
Only spells and spell-like abilities are subject to spell resistance. Extraordinary and supernatural abilities (including enhancement bonuses on magic weapons) are not. A creature can have some abilities that are subject to spell resistance and some that are not. In addition, some spells ignore spell resistance; see When Spell Resistance Applies, below.
Monsters attempting to use a spell or spell-like ability against a player character roll 1d20 + their Hit Dice, and compare that value against the target's Spell Resistance value. If the result equals or exceeds the target's Spell Resistance, the spell works. If it does not, the spell (and the action to cast it) are wasted, having no effect on the target.
A creature can voluntarily lower its spell resistance. Doing so usually requires a Standard Action that does not provoke an Attack of Opportunity. Once a creature lowers its resistance, it remains down until the creature's next turn. At the beginning of the creature's next turn, the creature's spell resistance automatically returns unless the creature intentionally keeps it down (requiring a new standard action each round).
A creature's spell resistance never interferes with its own spells, items, or abilities.
A creature with spell resistance cannot impart this power to others by touching them or standing in their midst. Only the rarest of creatures and a few magic items have the ability to bestow spell resistance upon another.
Spell resistance does not stack. If a creature has more than one source of Spell Resistance, only the highest available value is used.
When Spell Resistance Applies
- Each spell includes an entry that indicates whether spell resistance applies to the spell. In general, whether spell resistance applies depends on what the spell does.
- Spell resistance applies if the spell is targeted at the creature. Some individually targeted spells can be directed at several creatures simultaneously. In such cases, a creature's spell resistance applies only to the portion of the spell actually targeted at it. If several different resistant creatures are subjected to such a spell, each checks its spell resistance separately.
- If a spell uses the terms "object" or "harmless", they mean the same thing for spell resistance as they do for saving throws. A creature with spell resistance must voluntarily lower the resistance (a standard action) in order to be affected by such spells without forcing the caster to make a Caster Check.
- Spell resistance applies if the resistant creature is within the spell's area. It protects the resistant creature without affecting the spell itself.
- Most effect spells summon or create something and are not subject to spell resistance. Sometimes, however, spell resistance applies to effect spells, usually to those that act upon a creature more or less directly, such as web.
- Spell resistance can protect a creature from a spell that has already been cast. Check spell resistance when the creature is first affected by the spell.
- Check spell resistance only once for any particular casting of a spell or use of a spell-like ability. If spell resistance fails the first time, it fails each time the creature encounters that same casting of the spell. Likewise, if the spell resistance succeeds the first time, it always succeeds. If the creature has voluntarily lowered its spell resistance and is then subjected to a spell, the creature still has a single chance to resist that spell later, when its spell resistance is back up.
- Spell resistance has no effect unless the energy created or released by the spell actually goes to work on the resistant creature's mind or body. If the spell acts on anything else and the creature is affected as a consequence, no roll is required. Spell-resistant creatures can be harmed by a spell when they are not being directly affected.
- Spell resistance does not apply if an effect fools the creature's senses or reveals something about the creature.
- Magic actually has to be working for spell resistance to apply. Spells that have instantaneous durations but lasting results aren't subject to spell resistance unless the resistant creature is exposed to the spell the instant it is cast.
Successful Spell Resistance
- Spell resistance prevents a spell or a spell-like ability from affecting or harming the resistant creature, but it never removes a magical effect from another creature or negates a spell's effect on another creature. Spell resistance prevents a spell from disrupting another spell.
- Against an ongoing spell that has already been cast, a failed check against spell resistance allows the resistant creature to ignore any effect the spell might have. The magic continues to affect others normally.