Innate Spellcasting (Psionics). The adolescent brain’s innate spellcasting ability is Intelligence (spell save DC 16). It can innately cast the following spells, requiring no components:

At will: detect thoughts, levitate

1/day each: dominate beast, misty step

Legendary Resistance (3/Day). If the adolescent brain fails a saving throw, it can choose to succeed instead.

Magic Resistance. The adolescent brain has advantage on saving throws against spells and other magical effects.

Telepathic Hub. The adolescent brain can use its telepathy to initiate and maintain telepathic conversations with up to ten creatures at a time. The adolescent brain can let those creatures telepathically hear each other while connected in this way.

Tentacle. Melee Weapon Attack: +5 to hit, reach 30 ft., one target. Hit: 11 (2d8 + 2) bludgeoning damage.

Mind Blast (Recharge 5–6). The adolescent brain magically emits psychic energy. Creatures of the adolescent brain’s choice within 60 feet of it must succeed on a DC 16 Intelligence saving throw or take 23 (3d8 + 5) psychic damage and be stunned for 1 minute. A target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. 

The adolescent brain can take 3 legendary actions, choosing from the options below. It can take only one legendary action at a time and only at the end of another creature’s turn. The adolescent brain regains spent legendary actions at the start of its turn.

Tentacle. The adolescent brain makes a tentacle attack..