Hydroloth (5.5)

Medium Fiend (Yugoloth), Typically Neutral Evil
Armor Class 15
Hit Points 135 (18d8 + 54)
Speed 20 ft., swim 40 ft.
STR
12 (+1)
DEX
21 (+5)
CON
16 (+3)
INT
19 (+4)
WIS
10 (+0)
CHA
14 (+2)
Skills Insight +4, Perception +4
Damage vulnerabilities fire
Damage Resistances cold, lightning; bludgeoning, piercing, and slashing from nonmagical attacks
Damage Immunities acid, poison
Condition Immunities poisoned
Senses blindsight 60 ft., darkvision 60 ft., passive Perception 14
Languages Abyssal, Infernal, telepathy 60 ft.
Challenge 9 (5000 XP)     Proficiency Bonus +4
Amphibious.
Magic Resistance.
Secure Memory.
Watery Advantage.
ACTIONS
Multiattack.
Bite.
Claw.
Spellcasting.
Steal Memory (1/Day).
Teleport.

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

Monsters of the Multiverse
Hydroloth (5.5)