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.
The souls of fallen soldiers, mercenaries, and bodyguards who served evil without reservation often find everlasting servitude in the Nine Hells as merregons. These faceless foot soldiers are the Hells' legionnaires, tasked with protecting their infernal plane and its rulers against intruders.