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

Innate Spellcasting (Psionics). The mind flayer is a 10th-level spellcaster. Its innate spellcasting ability is Intelligence (spell save DC 15; +7 to hit with spell attacks). It can innately cast the following spells, requiring no components:

At will: guidance, mage hand, vicious mockery, true strike, detect thoughts, levitate

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

1st level (4 slots): charm person, command, comprehend languages, sanctuary

2nd level (3 slots): crown of madness, phantasmal force, see invisibility

3rd level (3 slots): clairvoyance, fear, meld into stone

4th level (3 slots): confusion, stone shape

5th level (2 slots): scrying, telekinesis

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.