Huge monstrosity, unaligned

Armor Class: 14 (Natural Armor)

Hit Points: 69 (6d12+30) 6d12+30

Speed: 30 ft , fly: 0 ft , swim: 30 ft

STR

19 +4

DEX

12 +1

CON

20 +5

INT

5 -3

WIS

10 +0

CHA

7 -2

Skills: Perception +4

Damage Immunities: acid

Condition Immunities: blinded, charmed, deafened, frightened, stunned

Senses: darkvision 60 ft., passive Perception 14

Challenge Rating: 4 (1100 XP)

Actions

Multiattack. The thessalhydra makes one maw attack and one Flurry of Bites.   Flurry of Bites. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 7 (1d6 + 4) 1d6+4 piercing damage plus 10 (4d4) 4d4 poison damage.   Maw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 9 (1d10 + 4) 1d10+4 piercing damage plus 5 (1d10) 1d10 acid damage.   Tail Pincer. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 10 (1d12 + 4) 1d12+4 slashing damage, and the target is grappled. As an action, the target can escape the grapple by succeeding on a DC 14 Strength (Athletics) or Dexterity (Acrobatics) check (its choice). Until this grapple ends, the thessalhydra can't use its tail pincer.   Acid Saliva (Recharge 5–6). The thessalhydra spits a glob of acid at a point it can see within 30 feet of it. Each creature within 10 feet of that point must make a DC 15 Dexterity saving throw, taking 18 (4d8) 4d8 acid damage on a failed save, or half as much damage on a successful one.

Legendary Actions

Legendary Actions The thessalhydra can take 2 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. The thessalhydra regains spent legendary actions at the start of its turn.   Detect. The thessalhydra makes a Wisdom (Perception) check with advantage.   Tail Swipe. The thessalhydra makes a tail pincer attack.