Armor Class 16 (natural armor)
Hit Points 45 (6d8 + 18)
Speed 30 ft.
Damage Resistances cold, [object Object]
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
Devil's Sight. Magical darkness doesn't impede the merregon's darkvision.
Magic Resistance. The merregon has advantage on saving throws against spells and other magical effects.
Multiattack. The merregon makes three Halberd attacks.
Halberd. Melee Weapon Attack: +6 to hit, reach 10 ft., one target. Hit: 9 (1d10 + 4) slashing damage.
Heavy Crossbow. Ranged Weapon Attack: +4 to hit, range 100/400 ft., one target. Hit: 7 (1d10 + 2) piercing damage.
Loyal Bodyguard. When another Fiend within 5 feet of the merregon is hit by an attack roll, the merregon causes itself to be hit instead.
Mordenkainen Presents: Monsters of the Multiverse, p. 179