Mind Flayer Dragonthrall

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

Innate Spellcasting (Psionics). The mind flayer’s innate spellcasting ability is Intelligence (spell save DC 15). It can innately cast the following spells, requiring no components:

At will: detect thoughts, levitate, suggestion, telekinesis

4/day: dominate monster

Multiattack. The dragonthrall can use its Frightful Presence. It then makes three attacks: one with its bite and two with its claws.

Claw. Melee Weapon Attack: +12 to hit, reach 5 ft., one target. Hit: 14 (2d6 + 7) slashing damage.

Tentacles. Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit: 15 (3d10 + 5) psychic damage. If the target is Medium or smaller, it is grappled (escape DC 15) and must succeed on a DC 15 Intelligence saving throw or be stunned until this grapple ends.

Extract Brain. Melee Weapon Attack: +12 to hit, reach 5 ft., one incapacitated humanoid grappled by the mind flayer. Hit: The target takes 75 (14d10) piercing damage. If this damage reduces the target to 0 hit points, the mind flayer kills the target by extracting and devouring its brain.

Frightful Presence. Each creature of the dragonthrall’s choice that is within 120 feet of the dragon and aware of it must succeed on a DC 18 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 dragon's Frightful Presence for the next 24 hours.

Breath Weapon (recharge 6). The dragon exhales it’s weapon in a 90- foot line that is 5 feet wide. Each creature in that line must make a DC 20 Dexterity saving throw, taking 66 (20d8) damage of the appropriate type (depending on the dragon’s variant before possession) on a failed save, or half as much damage on a successful one.

The dragon can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The dragon regains spent legendary actions at the start of its turn.

Detect. The mind flayer makes a Wisdom (Perception) check.

Tail Attack. The mind flayer makes a tail attack.

Wing Attack (Costs 2 Actions). The dragonthrall beats its wings. Each creature within 10 feet of the dragon must succeed on a DC 20 Dexterity saving throw or take 14 (2d6 + 7) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.