Ancient Aberrant Dragon

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

Creature Sense. The dragon is aware of the presence of creatures within 2 miles of it that have an Intelligence score of 4 or higher. It knows the distance and direction to each creature, as well as each creature's intelligence score, but can't sense anything else about it. A creature protected by a mind blank spell, a nondetection spell, or similar magic can't be perceived in this manner.

Innate Spellcasting (Psionics). 

The dragon's innate spellcasting ability is Intelligence (spell save DC 24). It can innately cast the following spells, requiring no components:

• At will: detect thoughts, levitate
• 1/day each: confusion, dominate monster, eyebite, feeblemind, mass suggestion, plane shift (self only), project image, scrying, telekinesis

Multiattack. The dragon can use its Frightful Presence. It then makes two attacks with its claws and one with a tentacle.

Claw. Melee Weapon Attack: +17 to hit, reach 5 ft., one target. Hit: 17 (2d6 + 10) slashing damage.

Tentacle. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hit: 26 (3d10 + 10) slashing damage. If the target is a Medium or smaller creature, it is grappled  (escape DC 22), pulled into an unoccupied space within 5 feet of the dragon, and is restrained until this grapple ends. The dragon can't use the same tentacle on another target until this grapple ends. The dragon has four tentacles.

Frightful Presence. Each creature of the dragon's choice that is within 120 feet of the dragon and aware of it must succeed on a DC 24 Wisdom saving throw or become frightened 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. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Frightful Presence for the next 24 hours.

Acid Breath (Recharge 5–6). The dragon exhales acid in a 60-foot cone. Each creature in that area must make a DC 22 Dexterity saving throw, taking 91 (26d6) acid damage on a failed save, or half as much damage on a successful one.

Mind Blast (Recharge 5–6). The dragon magically emits psychic energy in a 60-foot cone. Each creature in that area must succeed on a DC 22 Intelligence saving throw or take 27 (5d8 + 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.

Extract Brain. Melee Weapon Attack: +17 to hit, reach 5 ft., one incapacitated humanoid grappled by the dragon. Hit: 82 (15d10) piercing damage. If this damage reduces the target to 0 hit points, the dragon kills the target by extracting and devouring its brain.

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

Tentacle. The dragon makes a tentacle attack.

Wing Attack (Costs 2 Actions). The dragon beats its wings. Each creature within 10 feet of the dragon must succeed on a DC 25 Dexterity saving throw or take 17 (2d6 + 10) bludgeoning damage and be knocked prone. The dragon can then fly up to half its flying speed.