Dragon fire is the classic example, but a breath weapon can be a cloud of poisonous gas, a bolt of lightning, or a stream of acid. Breath weapons are usually supernatural abilities, and a creature needn’t be able to breathe to use one.
USING A BREATH WEAPON
When using a breath weapon, a creature is actually expelling something from its mouth rather than conjuring it by means of a spell or some other magical effect. Most creatures that have breath weapons are limited to a number of uses per day or by a minimum length of time that must pass between uses. Even if a creature has more than one type of breath weapon, the time between uses is a time during which it can’t use any of its breath weapons.
Using a breath weapon is typically a standard action. No attack roll is necessary. The breath simply fills its stated area, which is usually defined like a spell’s area. Any creature caught in the area must succeed on the appropriate saving throw or suffer the breath weapon’s full effect.
SAVES AGAINST BREATH WEAPONS
Breath weapons that deal energy damage allow a Reflex save for half damage (DC 10 + 1/2 breathing creature’s racial HD + its Con modifier; the exact DC is given in the creature’s descriptive text). Some breath weapons allow a Fortitude save or a Will save instead of a Ref ex save. In many cases, a creature that succeeds on its saving throw against such a breath weapon suffers a reduced effect.
Creatures are immune to their own breath weapons.