Armor Class 18 (natural armor)
Hit Points 253 (22d12 + 110)
Speed 40 ft., swim 80 ft.
STR
22 (+6)
DEX
10 (+0)
CON
20 (+5)
INT
14 (+2)
WIS
18 (+4)
CHA
18 (+4)
Saving Throws Dex +6, Cha +10
Skills History +8, Perception +10
Damage Resistances cold, fire; bludgeoning, piercing, and slashing from nonmagical attacks
Damage Immunities acid, poison
Condition Immunities exhaustion, poisoned
Senses truesight 120 ft., passive Perception 20
Languages all, telepathy 120 ft.
Challenge 17 (18000 XP)
Proficiency Bonus +6
Legendary Resistance (4/Day).
Regeneration.
Shrouded Being.
Slimy Demise.
Multiattack.
Barbed Tentacle.
Bite.
Gore.
Slime Wave.
Defiant Essence.
Slime Spray.