Merregon

Medium fiend (devil), lawful evil
Armor Class 16 (natural armor)
Hit Points 45 (6d8 + 18)
Speed 30 ft.
STR
18 (+4)
DEX
14 (+2)
CON
17 (+3)
INT
6 (-2)
WIS
12 (+1)
CHA
8 (-1)
Damage Resistances cold; bludgeoning, piercing, and slashing from nonmagical attacks that aren't silvered
Damage Immunities fire, poison
Condition Immunities frightened, poisoned
Senses darkvision 60 ft., passive Perception 11
Languages understands Infernal but can't speak, telepathy 120 ft.
Challenge 4 (1100 XP)
Devil's Sight.
Magic Resistance.
ACTIONS
Multiattack.
Halberd.
Heavy Crossbow.
REACTIONS
Loyal Bodyguard.

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

Mordenkainen´s Tome of Foes
Merregon