Thessalhydra (CR 18)
Gargantuan aberration
Init 25; Senses darkvision, scent; Notice 46
AC 33, flat-footed 18
(+15 Dex, +12 natural, –4 size)
HP 310 (20d8+220); fast healing 15
Fort +17, Ref +21, Will +19
Defensive Abilities all-around vision; Immune acid
Speed 40 ft., swim 20 ft.
Melee bite +27 (3d6+10/18–20 plus 2d6 acid), 8 snake bites +27 (1d8+10/18–20 plus 1d6 acid), pincer +26 (2d8+10 plus grab)
Ranged 8 acid spits +26 (2d6 acid)
Space 20 ft.; Reach 20 ft. (30 ft. with snake bites, 40 ft. with pincer)
Special Attacks breath weapon (160-ft. line, 20d6 acid damage, Reflex DC 31 half, usable every 1d4 rounds), constrict (2d6+10), pounce
Str 31, Dex 40, Con 32, Int 2, Wis 24, Cha 9
Base Atk +15; CMB +29; CMD 54 (58 vs. trip)
Combat Manuevers +4 grapple
Feats Bleeding Critical (F-DC 25), Combat Reflexes, Critical Focus, Improved Critical (bite, snake bites), Multiattack, Skill Focus (Perception), Weapon Finesse, Weapon Focus (bite, snake bites)
Skills Athletics +33, Perception +36
Environment marsh
Organization solitary
Treasure Value 20d6 gp
Special Abilities
Acid Spit (Su; acid; Con) As a standard action, a thessalhydra can spit acid from its eight snake mouths, making eight ranged attacks at any number of targets within a range of 120 feet. On a hit, an acid spit deals 2d6 points of acid damage. A creature hit by multiple acid spits from a single thessalhydra in 1 round takes the damage as if from one source for the purposes of applying acid resistance. For example, a creature hit by eight acid spits would take 16d6 points of acid damage, not 2d6 points of acid damage eight times. A creature critically hit by acid spit must succeed at a DC 31 Reflex save to avoid being blinded for 1 round by the acid.
Snake Bite (Ex) A thessalhydra’s serpent heads strike as secondary attacks that deal piercing and slashing damage plus an additional 1d6 points of acid damage.

The dreaded thessalhydra is a fearsome predator that has an unexpected agility. Despite its lumbering shape and looming size, the monster’s nimbleness makes it almost beautiful as it attacks. Thessalhydras are relatively rare, though their notorious speed and savagery have featured in countless legends. They are often whispered of in fear and awe by willful children in rural areas, whose exasperated parents have warned them to “be good, or the thessalhydra will pluck you out of your bed through the window when you sleep!”

A thessalhydra is 40 feet long, with its pincer-tipped tail adding another 30 feet to its overall length.

OPEN GAME LICENSE Version 1.0a - All text is Open Game Content.