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:

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

Magic Resistance.

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

Actions

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.

Environment: Underdark

Mind Flayer Psion