Aberrant Bone Devil

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

Illithid Skin. If a creature attempts to attack the aberrant devil while within 5 ft. of it, the creature must succeed a DC 16 Dexterity saving throw or be grappled by its tentacles. 

Innumerable Tentacles. The aberrant devil can grapple as many creatures as it can reach, however it has disadvantage on opposed grappling checks while restraining more than two creatures at a time.

Multiattack. The aberrant devil makes two Tentacle attacks and one Neurotoxin Sting attack.

Tentacle. Melee Attack Roll: +8, reach 10 ft. Hit: 11 (2d6 + 4) Bludgeoning damage.

Neurotoxin Sting. Melee Attack Roll: +8, reach 10 ft. Hit: 15 (2d10 + 4) Piercing damage. The target must succeed a DC 15 Constitution saving throw or take (4d8) Poison damage, and become Poisoned and Frightened until the start of the devil’s next turn. While Poisoned, the target has disadvantage on Strength rolls.

Consume Brain. If a creature that the aberrant devil is grappling dies, the devil consumes its brain, regaining 4d4 hit points. Any other creature that is being grappled by the aberrant devil must succeed a DC 15 Wisdom saving throw or be Frightened until it escapes the devil's grapple.