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

1/day each: dominate monster, plane shift (self only)

Spellcasting. The mind flayer is a 10th-level spellcaster. Its spellcasting ability is Intelligence (save DC 15, +7 to hit with spell attacks). The mind flayer has the following wizard spells prepared:

Cantrips (at will): blade ward, dancing lights, mage hand, shocking grasp

1st level (4 slots): detect magic, disguise self, shield, sleep

2nd level (3 slots): blur, invisibility, ray of enfeeblement

3rd level (3 slots): clairvoyance, lightning bolt, sending

4th level (3 slots): confusion, hallucinatory terrain

5th level (2 slots): telekinesis, wall of force

Tentacles. Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit:15 (2d10 + 4) 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: +7 to hit, reach 5 ft., one incapacitated humanoid grappled by the mind flayer. Hit:The target takes 55 (10d10) piercing damage. If this damage reduces the target to 0 hit points, the mind flayer kills the target by extracting and devouring its brain.

Mind Blast (Recharge 5–6). The mind flayer magically emits psychic energy in a 60-foot cone. Each creature in that area must succeed on a DC 15 Intelligence saving throw or take 22 (4d8 + 4) psychic damage and be stunned 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.