Multiattack

The hydra makes as many Bite attacks as it has heads.

Bite

_Melee Weapon Attack:_ +8 to hit, reach 10 ft., one target. _Hit:_ 10 (1d10+5) piercing damage.

Noxious Breath (Recharge Special)

The hydra exhales poisonous gas in a 30-foot cone. Each creature in that area must make a DC 16 CON save, taking 40 (9d8) poison damage on a failed save, or half as much damage on a successful one. While the hydra has five or more heads, this action has a recharge of 6. The recharge range increases for each head the hydra has below five. For example, a hydra that starts its turn with two heads can recharge this feature on a 3, 4, 5, or 6.