Encounters by Locale: Storm Horns and Thunder Peaks - Cave, Lower Levels
Cryohydra, Nine-Headed (CR 10)
AC: 15 (-2 size, +1 Dex, +6 natural), touch 9, flat-footed 14
Hit Dice: 9d10+48 (97 hp)
Fort +11, Ref +7, Will +5
Speed: 20 ft., swim 20 ft.
Space: 15 ft./10 ft.
Base Attack +9; Grapple +22
Attack: 9 bites +13 melee
Full Attack: 9 bites +13 melee
Damage: Bite 1d10+5
Special Attacks: Breath weapon
Abilities: Str 21, Dex 12, Con 20, Int 2, Wis 10, Cha 9
Special Qualities: fast healing 19, cold immunity, vulnerable to fire
Feats: Blind-fight; Combat Reflexes; Iron Will; Toughness; Weapon Focus (bite)
Skills: Listen +8, Spot +8, and Swim +13
Climate/Terrain: Cold marsh and underground
Treasure: 1/10 coins, 50% goods, 50% items
Source: Monster Manual
Hydras can attack with all their heads at no penalty, even if they move or charge during the round.
These 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.
Cold Subtype (Ex): Cold immunity; double damage from fire except on a successful save.
Skills: Hydras receive a +2 racial bonus to Listen and Spot checks, thanks to their multiple heads.
Feats: A hydra's Combat Reflexes feat allows it to use all its heads for attacks of opportunity each round.