Homebrew, The Ninth World
Innate Spellcasting (Psionics). The mind flayer’s innate spellcasting ability is Intelligence (spell save DC 18). It can innately manifest the following spells, requiring no components:
Magic resistance. The mindflayer has Advantage on Saving Throws against spells and other magical effects.
Multiattack. The mind flayer uses Mind Shackle and then makes two Tentacle attacks.
Tentacles. Melee Weapon Attack: 1d20+9 to hit, reach 5 ft., one target. Hit:
2d10+5 psychic damage. If the target is Medium or smaller, the mind flayer may grapple the target (escape DC 18) and must succeed on a DC 18 Intelligence saving trow or be stunned until this grapple ends.
Extract Brain. Melee Weapon Attack: 1d20+9 to hit, reach 5 ft., one incapacitated humanoid grappled by the mindflayer. Hit:
10d10+4 piercing damage. If this damage reduces the target to 0 HP, the mindflayer kills the target by extracting and devouring its brain.
Mind Shackle (Recharge 6). The mind flayer releases a scarab - a small scarab like construct - which seeks out a target to dominate. The target must make a DC 18 Wisdom saving throw or become charmed as the dominate monster spell. Each time a target saves against this ability, Mind Shackle recharges.
Mind Blast (Recharge 5-6). The mind flayer psionically emits psychic energy in a 60-foot cone. Each creature in that area must succeed on a DC 18 Intelligence saving throw or take
4d8+5 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.
Bonus Action
Psionics. The mind flayer is a 10th-level spellcaster. Its spellcasting ability is Intelligence (save DC 18, 1d20+10 to hit with spell attacks). The mind flayer has the following psionic abilities (spells) prepared:
Psionic Counter. As a reaction to a creature manifesting a psionic power, the mind flayer can use his reaction to cancel the effect by spending a spell slot of equal level of the manifested power.