Bone Devil Taskmaster

Aura of Tyranny. An ally that is within 30 feet of the devil and can see and hear the devil and has less hit points than the devil has advantage to saving throws against being charmed and frightened, provided that the devil isn't incapacitated.

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.

Multiattack. The devil can use its Frightful Presence. It then makes two Claw attacks and one Sting attack.

Claw. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 9 (1d8 + 5) slashing damage.

Sting. Melee Weapon Attack: +9 to hit, reach 10 ft., one target. Hit: 14 (2d8 + 5) piercing damage plus 21 (6d6) poison damage and the target must succeed on a DC 16 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.

Frightful Presence. Each creature of the devil's choice that is within 120 feet of the devil and aware of it must succeed on a DC 16 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the devil's Frightful Presence for the next 24 hours.

Spellcasting. The devil casts one of the following spells, requiring no material components and using Charisma as the spellcasting ability (spell save DC 16):

3/day each: invisibility (self only), major image
1/day: teleport, wall of ice

Spur Ally. The devil targets one ally within 30 feet that can see and hear the devil and must have less hit points than the devil. The target takes 3 (1d6) psychic damage and must use its reaction to make one melee weapon attack with advantage on the attack roll.