Damage Resistance and Vulnerability

Some creatures and objects are exceedingly difficult or unusually easy to hurt with certain types of damage.

If a creature has resistance to a damage type, damage taken of that type is reduced by 5 + their Level/CR to a maximum of -20. If a creature has vulnerability to a damage type, damage taken of that type is increased by 20 - their Level/CR to a maximum of +5.

If an object has resistance to a damage type, damage taken of that type is halved. If an object has vulnerability to a damage type, damage taken of that type is doubled.

Resistance and then vulnerability are applied after all other modifiers to damage. For example, a creature has resistance to bludgeoning damage and is hit by an attack that deals 25 bludgeoning damage. The creature is also within a magical aura that reduces all damage by 5. The 25 damage is first reduced by 5 and then halved, so the creature takes 10 damage.

For a creature, multiple instances of resistance or vulnerability that affect the same damage type stack additively. For example, if a creature has -5 resistance to fire damage as well as -5 resistance to all nonmagical damage, the damage of a nonmagical fire is reduced by -10 against the creature.

For an object, multiple instances of resistance or vulnerability that affect the same damage type stack. For example, if an object has vulnerability to fire damage as well as vulnerability to all nonmagical damage, the damage of a nonmagical fire is increased by 3/4 against the object.