Some creatures will be immune to certain effects. These immunities will be listed in their special defenses in the creature stat block. Immunity means there is no effect.
Some creatures will have a resistance to an effect that is not total immunity. These resistances come it three forms: Weapon Damage Resistance, General Resistance, and Magic Resistance.
Some creatures will be immune to weapons without magical enchantments (e.g. a +1 long sword). Some will require enchantments to be higher than “+1”.
In a creature’s statistics, this is damage resistance is found in Special Defenses and will be noted as: “DR/(magical bonus)”. Thus, an elemental requiring weapons with a minimum of +2 enchantment level to affect them: "DR/+2". This means the creature is immune to damage from mundane weapons and weapons under the designated magical enhancement. However, certain creatures will be able to crack through this resistance due to the power of their attacks (related to hit dice).
This ability is tied to hit dice and not related to character class, so any hit dice granted by character class levels are ignored in this specific case.
Creatures able to bypass weapon damage resistance can do so with any weapon.
Special Material Requirement. Sometimes special materials will be required to damage a creature. This will be noted as "DR/<magical bonus or material type>". When a creature can only be hit by magic weapons OR a special material, both will be listed with an "or". An "and" means both magic AND the special material must be present to do damage. For example, many lycanthropes require either magic or silver to damage them, listed as: "DR/+1 or silver".
Special Weapon Type Resistance. Sometimes, creatures will be immune or will take less damage from certain weapon types. If so, the weapon types listed will be listed along with the amount of resistance. If no amount is listed, the resistance should be considered as total. Examples: "DR/blunt (half)" means the creature takes half damage from blunt weapons. "DR/piercing (1 point)" means the creature will take a maximum of 1 point of damage from piercing weapons. "DR/piercing" means the creature is immune to piercing weapons. While it may be confusing to list weapon types thusly, it's generally easier to list what does not harm versus what does harm in this case. In an unlikely case where a weapon type and material is required, the material will always be listed first: "DR/silver and piercing" means only piercing weapons made of silver will affect the creature.
If a magic plus is listed and effect in parenthesis, it means weapons of up to that bonus are affected and weapon over that bonus do normal damage. Thus, damage resistance of "DR/+2 (half damage) means magic weapons of up to +2 magical bonus do half damage (and it's inferred that non-magical weapons do no damage). Weapons of +3 bonus or above do normal damage.
A dash means the resistance is against any weapon of any type. Thus a magic-user protected by a stoneskin spell will have: "DR/- (1 attack routine)" which means total immunity from damage from one attack routine (which then discharges the spell).
Visible Effects of Weapon Immunity. Those attacking a creature with total immunity to the weapon type being used will note this one round after the first successful strike (at the end of that round). Any partial resistance to a weapon will not be noticeable in normal circumstances.
Some creatures will be partially resistant or have a chance to be wholly resistant to a listed effect. This will be listed under Special Defenses and will be noted: "Resist [effect; save modifier or chance to resist if not 100%]".
Thus an elf has a 90% chance to fully resist a sleep or charm effect: "resist [sleep, charm; 90%]"; A creature that takes half damage from fire: "resist [fire; half]".
A creature immune to something will have this listed in Special Defenses: "immune to (effects listed)". Thus, a creature immune to poison and stunning will have: "immune to poison and stunning" listed.
Unlike magic resistance, a creature with a listed resistance or immunity cannot drop this protection.
Magic resistance is an ability possessed by certain creatures that causes magic to fail with regards to effects on them. Typically, this only includes direct effects.
Magic resistance is given as a percentage. This is the chance that the magic cannot affect the protected creature.
When a magic effect comes into contact with a creature with magic resistance, a magic resistance check (d%) is rolled, adjusted by +5% per caster level. If the result is over the resisstance value, the creature's resistance is overcome and is affected by the magic normally.
Thus, if a creature with 100% magic resistance is targeted by a lightning bolt cast by a 10th level magic-user (5 * 10 = +50), a check result of 50+ will overcome the creature's resistance and the creature must save versus the spell. If the check result is under 50, the creature is totally unaffected by the lightning bolt, although others ahead or behind will be affected (a spell is only cancelled if it solely targets the resistant creature).
A successful magic resistance roll means:
The Magic Fails—because the effect targeted only the creature with magic resistance.
The Magic Works but Fails to Affect Only the Creature with Resistance—All others in the area of effect are affected normally. Permanent effects or triggered effects are suppressed while the creature with resistance interacts with them. See examples below.
Spells descriptions will normally indicate how they perform against a magic resistant foe.
Magical effects that change the environment or terrain cannot be resisted. This includes weather effects (although see examples below). Example. The spells earthquake or transmute rock to mud.
Indirect effects on light or vision cannot be resisted. Ex. magical darkness (not cast directly on the creature with magic resistance), fog cloud, obscurement, or invisibility. A wall of fire may cause no damage, but it may not be able to be seen through. Similarly, a web spell may be able to be passed without becoming entangled, but the creature cannot see through it.
Illusions that are visual or audible cannot be resisted. If physical contact is made, or any direct effect occurs, the illusion can be resisted.
Secondary non-magical effects cannot be resisted. For example, a fireball that causes a fire and resultant smoke. Contact with non-magical fire and inhaling non-magical smoke will have normal effects.
Mundane objects launched as missiles via magic cannot be resisted. Example. Damage due to objects thrown or dropped using telekinesis.
Summoned creatures cannot be resisted. Example. A summoned creature can make melee attacks against a creature with magic resistance.
Objects created by magic with a duration of “instantaneous” cannot be resisted.
In general, extra-dimensional spaces are not affected by magic resistant creatures.
Magical weapons with pluses cannot be resisted. For example, a +1 sword still functions as such and can cause damage and cut a creature with magic resistance.
Certain innate magical-seeming attacks by creatures cannot be resisted. In particular, supernatural innate abilities that cause energy drain, ability damage/drain, aging, disease, petrification, paralysis, or poison effects cannot be resisted. Certain fear-based innate abilities (related to touch attacks) or others may not be resisted per the creature’s description or ruling from the GM. Like effects from magic items can always be resisted.
The effects of protection from evil or good spells (of any type) cast on another creature cannot be resisted by conjured or summoned creatures with magic resistance. However, creatures not conjured or summoned can attempt to shatter the ward using magic resistance—See Active Resistance below.
Spells, spell-like, or innate abilities cast as spells that target or otherwise directly affect the creature with magic resistance. Examples. A magic missile spell (any missiles targeting the resistant creature fail), a light spell targeting the creature’s eyes (spell fails totally), a rod of beguiling effect (others may be affected but not the resistant creature), or damage from a wall of fire from a wand of fire (others may be affected but not the resistant creature).
Permanent area effects are resisted (ignored, treated as if not there); See also How Magic Resistance Works below.
Within the limitations given above, magic resistance works in three modes:
Passive Resistance. (continuous)
This is always-on and all external magic is automatically resisted. External magic is defined as magic that comes from a source other than the magic resistant creature’s own (internal) spells, spell-like abilities, and innate abilities. This means a magic resistant creature can cast invisibility on itself, or use a spell-like ability to fly—without requiring a magic resistance check. However, to drink a potion of healing and have it take effect without a check, the creature must drop its protection.
A magic item possessed by a magic resistant creature and used to cast a spell (on itself) as an innate ability is NOT considered an internal ability and will be resisted unless the creature drops its protection as specified below.
Usually, only one magic resistance check is given for any one effect even if the effect is active for a period of time. For example, a wall of fire will burn those in the area of effect when cast and if a creature moves through the wall, it will take damage again. If the check fails to overcome a creatures magic resistance, the resistant creature can move through the wall without suffering any thermal effects (to themselves or anything carried when the check was made) for the duration of the spell. Smoke produced by burning objects near the wall and effects on vision due to the wall cannot be resisted.
Active Resistance. [innate] (major)
A magic resistant creature, encountering certain barriers or wards can choose to “shatter” the spell or magic effect using a major action. This will dispel the magic either permanently or for a time. Only spells or effects that note they can be so shattered in the description can be affected this way. Otherwise, magic resistance works as normal—the creature moving through or past as if the magic was not there (on a successful resistance check).
Dropping Protection. [innate] (major)
A magic resistant creature can voluntarily drop its protection as a major action by using an innate ability. Once complete, the creature will have no magic resistance until the end of the next round. After this time, the magic resistance will automatically re-enable. The creature with magic resistance can extend the time the resistance is dropped by using a minor action (innate) each round after the first to extend the effect for one round.
Items that do not directly affect a magic resistant creature will always work when used by a magic resistant creature normally. e.g. A +1 sword or wand of magic missiles targeting another creature will operate normally.
Certain non-direct effects can be implemented but will be resisted automatically (unless the magic resistant caster/wielder drops protection as per above). e.g. A fireball cast from a wand of fire will be resisted if the caster is in the area of effect. Note this will also affect beneficial magic (like the potion of healing example above).
Items with a non-activated, passive feature. These items must be donned while protection has been dropped. Once the resistance resumes, no checks are necessary for the item to work normally for the wearer. Examples are a ring of protection, ring of free action, boots of elvenkind, or a cloak of protection or items with like features. Some items have both passive features and active features. If the procedure is followed, the passive features will work normally. This class of items includes items that are trigger-based such as a ring of feather falling, a brooch of shielding or cloak of displacement.
Items with extra-dimensional spaces are unaffected by a creature's magic resistance (eg. a bag of holding).
Items with an activated feature targeting the possessor. For each use, protection must be dropped or a magic resistance check made for the effect to work. Examples are a ring of invisibility or boots of levitation. Some items are "engaged" rather than activated, such as a cloak of elvenkind. These items are considered non-activated as above (check with the GM).
Items requiring attunement. Assuming a magic resistant creature cannot drop protection for long enough to attune an item, a magic resistance check is made for each day (or fraction thereof) of attunement required. If a check fails to overcome the magic resistance the process must be begun again.
Examples. A 100% resistant creature wears a ring of invisibility. In order to activate it, the creature must first drop protection, then next round, activate the ring, otherwise, a magic resistance check of 41+ (d%) is required (given the ring’s caster level of 12) for the ring to function when activation is attempted. The same creature drops protection, dons a ring of free action, and after the end of the next round, resistance becomes operational again. The ring will continue to operate in perpetuity while worn.