Wastrilith (5.5)

Large Fiend (Demon), Typically Chaotic Evil
Armor Class 18 (natural armor)
Hit Points 157 (15d10 + 75)
Speed 30 ft., swim 80 ft.
STR
19 (+4)
DEX
18 (+4)
CON
21 (+5)
INT
19 (+4)
WIS
12 (+1)
CHA
14 (+2)
Saving Throws Str +9, Con +10
Damage Resistances cold, fire, lightning; bludgeoning, piercing, and slashing from nonmagical attacks
Damage Immunities poison
Condition Immunities poisoned
Senses darkvision 120 ft., passive Perception 11
Languages Abyssal, telepathy 120 ft.
Challenge 13 (10000 XP)     Proficiency Bonus +5
Amphibious.
Corrupt Water.
Magic Resistance.
ACTIONS
Multiattack.
Bite.
Claws.
Grasping Spout.
BONUS ACTIONS
Undertow.

This full creature's stat block is not available (not OGL).

Monsters of the Multiverse
Wastrilith (5.5)