Hold Breath. The pyrohydra can hold its breath for 1 hour.

Multiple Heads. The pyrohydra has 12 heads. While it has more than one head, the hydra has advantage on saving throws against being blinded, charmed, deafened, frightened, stunned, and knocked unconscious.

Whenever the pyrohydra takes 28 or more damage in a single turn, one of its heads dies. If all its heads die, the hydra dies.

At the end of its turn, it grows two heads for each of its heads that died since its last turn, unless it has taken cold damage since its last turn. The pyrohydra regains 10 hit points for each head regrown in this way.

Reactive Heads. For each head the pyrohydra has beyond one, it gets an extra reaction that can be used only for opportunity attacks.

Wakeful. While the pyrohydra sleeps, at least one of its heads is awake.

Multiattack. The pyrohydra makes as many bite attacks as it has heads.

Bite. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 10 (1d10 + 5) piercing damage.

Fire Breath (Recharge 5-6). The Pyrohydra exhales fire in a 60-foot line, 5-feet wide. Each creature in that area must make a DC 17 Dexterity saving throw, taking 10 (3d6) fire damage on a failed save, or half as much damage on a successful one. Regrown heads are automatically charged.