Akregon, Infernal Despair

Legendary Resistance (3/Day). If Akregon fails a saving throw, it can choose to succeed instead.

Absorbing Grasp.reach 5 ft., one target. Akregon attempts to grab and absorb a creature into its body. The creature must succeed on a DC21 strength saving throw or find some other means of escape amenable to the DM. After three turns, the creature is absorbed into Akregon, who gains 3D6 HP.

Abyssal Mist. Akregon emits a fetid black mist in a 60-foot sphere around itself. Any creature in range makes a DC16 Constitution saving throw, taking 31 (9D6) necrotic damage on a failed save, or half as much on a successful one. Creatures that fail the Constitution saving throw are also Blinded. 

Multiattack. Akregon makes four attacks: two with its bite (one per head) and two with its claws.

Bite. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 19 (2d10 + 8) piercing damage plus 7 (2d6) fire damage.

Claw. Melee Weapon Attack: +14 to hit, reach 5 ft., one target. Hit: 15 (2d6 + 8) slashing damage.

Black Flame Breath (Recharge 5–6). The dragon exhales fire in a 60-foot cone. Each creature in that area must make a DC 21 Dexterity saving throw, taking 63 (18d6) necrotic damage on a failed save, or half as much damage on a successful one.