Devil's Sight. Magical darkness doesn't impede the devil's darkvision.

Magic Resistance. The devil has advantage on saving throws against spells and other magical effects.

Bone Cocoon. Once per 60 days upon death the devil instead curls up, surrounded by a hard bone shell. The devil regains 5 hp per turn it is like this until fully healed or until all other allies are slain. Then it bursts out and is slowed. (-2 AC and disadvantage on DEX) Cocoon HP=50 AC=22.

Multiattack. The devil makes three attacks: two with its claws and one with its sting.

Claw. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 8 (1d8 + 4) slashing damage.

Sting. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 13 (2d8 + 4) piercing damage plus 17 (5d6) poison damage, and the target must succeed on a DC 14 Constitution saving throw or become poisoned for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Eyebite: For the spell's duration, your eyes become an inky void imbued with dread power. One creature of your choice within 60 feet of you that you can see must succeed on a Wisdom saving throw or be affected by one of the following effects of your choice for the duration. On each of your turns until the spell ends, you can use your action to target another creature but can't target a creature again if it has succeeded on a saving throw against this casting of eyebite.

Asleep. The target falls unconscious. It wakes up if it takes any damage or if another creature uses its action to shake the sleeper awake.

Panicked. The target is frightened of you. On each of its turns, the frightened creature must take the Dash action and move away  you by the safest and shortest available route, unless there is nowhere to move. If the target moves to a place at least 60 feet away from you where it can no longer see you, this effect ends.

Sickened. The target has disadvantage on attack rolls and ability checks. At the end of each of its turns, it can make another Wisdom saving throw. If it succeeds, the effect ends.