V'ulle, Scion of the Sentient Sea

Burrowing Power. Spells cast by V'ulle enter the Ethereal plane, bypassing any cover a target is using.

Psychic Defense. While V'ulle is wearing no armor and wielding no shield, its AC includes its Intelligence modifier.

Magic Resistance. V'ulle has advantage on saving throws against spells and other magical effects.

Unusual Nature. V'ulle does not require sleep.

Volatile Mind. When V'ulle succeeds on a saving throw against mind-affecting spells or spell-like effects, the source of the spell or effect takes 4 (1d8) psychic damage.

Water Dependency. V'ulle can only breathe water.

Dissipating Touch. Melee Spell Attack: +7 to hit, reach 5 ft., one target. Hit: 9 (2d8) thunder damage.

Mind Thrust. Ranged Spell Attack: +7 to hit, range 60 ft., one target. Hit: 11 (2d10) psychic damage.

Spellcasting (Psionics). V'ulle casts one of the following spells. requiring no spell components and using Intelligence as the spellcasting ability (save DC 15).

At Will: Mage Hand, Minor Illusion, Telekinesis, Vicious Mockery (2d4)
3/Day each: Charm Person (as a 5th level spell), Detect Thoughts, Hypnotic Pattern
1/Day each: Confusion, Dominate Monster, Stinking Cloud

Mass Deja Vu (Recharges after a Short or Long Rest). V'ulle chooses up to twelve creatures within 60 ft. of it that it can see. Each creature must succeed on a DC 15 Wisdom saving throw or it must repeat the actions it took on its previous turn. If the situation has changed in such a way that the creature is unable to take the same action again, the creature stands still and takes no actions until the end of its turn.

Biofeedback (Recharge 4-6). When V'ulle takes bludgeoning, piercing, or slashing damage, it toughens its body against incoming wounds, gaining resistance to the triggering damage type until the end of its next turn.

V'ulle can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time, and only at the end of another creature's turn. V'ulle regains spent legendary actions at the start of its turn.

Deceleration. V'ulle warps the space around one Medium or smaller creature within 30 ft. of it. That creature must succeed on a DC 15 Dexterity saving throw or have its speed halved until the end of V'ulle's next turn.

Recall Agony. The fabric of time parts to V'ulle's will, revealing wounds a creature within 120 ft. of it has received in the past (or has yet to receive). That creature must succeed on a DC 15 Constitution saving throw, taking 7 (2d6) psychic damage on a failure, or half as much on a success. If the saving throw fails by 5 or more, the target takes an additional 7 (2d6) psychic damage at the start of its next turn.

Daze (Costs 2 Actions). V'ulle clouds the mind of a creature within 30 ft. of it. That creature must succeed on a DC 15 Wisdom saving throw or be Incapacitated until the end of its next turn.

Cast a Spell (Costs 3 Actions). V'ulle uses Spellcasting.