Thessalhydra (5e Creature)
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Huge monstrosity (thessalmonster), neutral
Saving Throws Dex +6, Con +13, Cha +3
Multiple Heads. The thessalhydra has nine heads. While it has more than one head, the thessalhydra has advantage on saving throws against being blinded, charmed, deafened, frightened, stunned, and knocked unconscious, and enemies who flank it do not gain advantage on their attack rolls.
Reactive Heads. For each head the thessalhydra has beyond one, it gets an extra reaction that can be used only for opportunity attacks.
Wakeful. While the thessalhydra sleeps, at least one of its heads is awake.
Multiattack. The thessalhydra makes 8 bite attacks with its snake heads,1 hideous maw attack and one tail pincer attack.
Bite. Melee Weapon Attack: +13 to hit, reach 15 ft., one target. Hit:: 14 (2d6 + 7) piercing damage plus 11 (2d10) poison damage.
Hideous Maw. Melee Weapon Attack: +13 to hit, reach 10 ft., one target. Hit: 29 (4d10 + 7) piercing damage plus 11 (2d10) acid damage and the target must make a DC 21 Dexterity saving throw or their worn armor or shield has its AC reduced by 1d4. If the total bonus, including any lost magical bonuses is reduced to 10 or less, the armor or shield is destroyed.
Tail Pincer. Melee Weapon Attack: +13 to hit, reach 15 ft., one target. Hit: 18 (2d10 + 7) piercing damage plus the target must succeed on a DC 21 Strength saving throw or be moved to an unoccupied within the tail pincer's reach.
Acid Breath (Recharges after a Short or Long Rest). The thessalhydra breathes acid at a point it can see within 60 feet of it. Each creature in a 20-foot-radius sphere centered on that point must make a DC 21 Dexterity. On a failed save, a creature takes 66 (12d10) acid damage, the target worn armor or shield has its AC reduced by 1d4. If the total bonus, including any lost magical bonuses is reduced to 10 or less, the armor or shield is destroyed. On a successful save, the creature takes half as much damage and its armor is unaffected.
The thessalmonsters are a family of enigmatic hybrid monsters resembling hydras. The actual derivation of the name ”thessal” is unknown. Legends suggest that the name thessal referred to a person or organization responsible for the creation of these monstrosities, or the land where they were first encountered.