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Creatures with this extraordinary ability recover from wounds quickly and can even regrow or reattach severed body parts.
Damage dealt to the creature is treated as subdual damage, and the creature automatically cures itself of subdual damage at a fixed rate.
Certain attack forms, typically fire and acid, deal damage to the creature normally; that sort of damage doesn't convert to subdual damage and so doesn't go away. The creature's description includes the details.
These creatures can regrow lost portions of their bodies and can reattach severed limbs or body parts. Severed parts die if they are not reattached.
Regeneration does not restore hit points lost from starvation, thirst, or suffocation.
Attack forms that don't deal hit point damage (for example, disintegration and most poisons) ignore regeneration.
An attack that can cause instant death, such as a coup de grace, massive damage, or an assassin's death attack, only threatens the creature with death if it is delivered by weapons that deal it normal damage.