Multiple angry snake-like heads rise from the sleek, serpentine body of this terrifying monster.
Str 17, Dex 12, Con 18, Int 2, Wis 11, Cha 9
A hydra can be killed by severing all of its heads or slaying its body. Any attack that is not an attempt to sever a head affects the body, including area attacks or attacks that cause piercing or bludgeoning damage. To sever a head, an opponent must make a sunder attempt with a slashing weapon targeting a head. A head is considered a separate weapon with hardness 0 and hit points equal to the hydra’s HD. To sever a head, an opponent must inflict enough damage to reduce the head’s hit points to 0 or less. Severing a head deals damage to the hydra’s body equal to the hydra’s current HD. A hydra can’t attack with a severed head, but takes no other penalties.
When a pyrohydra’s head is destroyed, two heads regrow in 1d4 rounds. A pyrohydra cannot have more than twice its original number of heads at any one time. To prevent new heads from growing, at least 5 points of acid or cold damage must be dealt to the stump (a touch attack to hit) before they appear. Acid or cold damage from area attacks can affect stumps and the body simultaneously. A pyrohydra doesn’t die from losing its heads until all are cut off and the stumps seared by acid or fire.
A pyrohydra gains the fire subtype. Each of its heads has a breath weapon (15-ft. cone, 3d6 fire damage [pyrohydra], Reflex half) useable every 1d4 rounds. The save DC is 10 + 1/2 the pyrohydra’s HD + the pyrohydra’s Con modifier.
Cryohydra/Pyrohydra (+2 CR): Variants of the standard hydra, the cryohydra lives in cold marshes or on glaciers, while the pyrohydra prefers deserts or volcanic mountains. A cryohydra gains the cold subtype, while a pyrohydra gains the fire subtype. Each of its heads has a breath weapon (15-ft. cone, 3d6 cold damage [cryohydra] or 3d6 fire damage [pyrohydra], Reflex half) useable every 1d4 rounds. The save DC is 10 + 1/2 the hydra’s HD + the hydra’s Con modifier. Although fire attacks cannot prevent a pyrohydra’s neck stump from growing new heads (since it is immune to fire), 5 points of cold damage does. Acid works normally on both hydra variants.
You can make more powerful pyrohydras by increasing their Hit Dice—each added HD increases the pyrohydra’s statistics as appropriate, but also gives it one additional head and a +1 increase to its natural armor. A hydra’s CR increases by +1 for each Hit Die it gains.