These purplish hydras can breathe jets of frost 10 feet high, 10 feet wide, and 20 feet long. All heads breathe once every 1d4 rounds. Each jet deals 3d6 damage per head. A successful Reflex save halves the damage. The save DC is 10 + 1/2 hydra's original number of heads + the hydra's Constitution modifier.

Hydras can attack with all their heads at no penalty, even if they move or charge during the round. A hydra can be killed either by severing all its heads or by slaying its body. To sever a head, an opponent must hit the monster's neck with a slashing weapon and deal damage equal to the hydra's original hit point total, divided by its original number of heads, in one blow. (The player says where the attack is aimed just before making the attack roll.) For example, if a five-headed hydra has 52 hp, a single blow dealing 10 or more points of damage severs a head (52 / 5 = 10.4, rounded down to 10). Any excess damage is lost. A severed head dies, and a natural reflex seals the neck shut to prevent further blood loss. The hydra can no longer attack with the severed head but suffers no other penalties. A severed head regrows in about a month.