Amphibious. The aberrant mind can breathe air and water.

Corrupting Presence. Any plant that spends 24 within a mile of the aberrant mind must succeed on a DC 19 Constitution saving throw or begin to warp from the aberrant mind's presence. On a failed save, the plant grows thorns on its trunk and branches that deal 7 (2d6) piercing damage to any creature within 5 feet of it.

Any creature that spends more than 24 hours within 300 feet of the aberrant mind must succeed on a DC 19 Constitution saving throw or gain a level of exhaustion. The creature must repeat the saving throw every hour after the first 24. If the creature fails 5 saves, it doesn't die. It is instead transformed into a Berbalang, Choker, Gazer, Intellect Devourer, Nothic, or Spectator randomly. Roll 1d6 to determine what the creature is transformed into.

If the aberrant mind dies, the plants revert to normal after 3 (1d6) days only a wish spell can transform a creature back to its normal form.

 Innate Spellcasting (Psionics). The aberrant mind's innate spellcasting ability is Intelligence (spell save DC 19). It can innately cast the following spells, requiring no components:

At will: mind sliver

3/day each: detect thoughts, dissonant whispers, levitate, phantasmal force

1/day each: feeblemind, nondetection (self only), synaptic static

Magic Resistance. The aberrant mind has advantage on saving throws against spells and other magical effects. 

Legendary Resistance (2/Day). If the aberrant mind fails a saving throw, it can choose to succeed instead.

Probing Telepathy. If a creature communicates telepathically with the aberrant mind, the aberrant mind learns the creature's greatest desires and greatest fears.

Psychic Resilience. (Recharges after a Short or Long Rest). If the aberrant mind would be reduced to 0 hit points, its current hit point total resets to 100 hit points, recharges its Mind Blast, and it regains its Legendary Resistance. Additionally, the hollow one can now use the options in the"Mythic Actions" section for 1 hour. Award a party an additional 18,000 XP (36,000 XP total) for defeating the hollow one after its Psychic Resilience activates. 

Sunlight Hypersensitivity. The aberrant mind takes 10 (3d6) radiant damage when it starts its turn in sunlight. While in sunlight, it has disadvantage on attack rolls and ability checks.

Thrives in Darkness. The aberrant mind magically makes all trees under its control grow their branches to create an area of nonmagical darkness in a 120 foot radius sphere around the aberrant mind at all times. 

Multiattack. The aberrant mind makes two attacks with its tentacles and casts one spell that takes 1 action to cast or uses its eye rays.

Tentacles. Melee Weapon Attack: +11 to hit, reach 10 ft., one creature. Hit: 16 (2d10 + 5) psychic damage and the target must succeed on a DC 19 Intelligence saving throw or be stunned until the end of the aberrant mind's next turn.

Eye Rays. The aberrant mind shoots two of the following magical eye rays at random (reroll duplicates), choosing one to two targets it can see within 120 feet of it:

1. Charm Ray. The targeted creature must succeed on a DC 19 Wisdom saving throw or be charmed by the aberrant mind for 1 hour, or until the aberrant mind harms the creature.
2. Slowing Ray. The targeted creature must succeed on a DC 19 Dexterity saving throw. On a failed save, the target’s speed is halved for 1 minute. In addition, the creature can’t take reactions, and it can take either an action or a bonus action on its turn, not both. The creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
3. Enervation Ray. The targeted creature must make a DC 19 Constitution saving throw, taking 36 (8d8) necrotic damage on a failed save, or half as much damage on a successful one.
4. Telekinetic Ray. If the target is a creature, it must succeed on a DC 19 Strength saving throw or the aberrant mind moves it up to 30 feet in any direction. It is restrained by the ray’s telekinetic grip until the start of the aberrant mind's next turn or until the aberrant mind is incapacitated.
   If the target is an object weighing 300 pounds or less that isn’t being worn or carried, it is moved up to 30 feet in any direction. The aberrant mind can also exert fine control on objects with this ray, such as manipulating a simple tool or opening a door or a container.
5. Petrification Ray. The targeted creature must make a DC 19 Dexterity saving throw. On a failed save, the creature begins to turn to stone and is restrained. It must repeat the saving throw at the end of its next turn. On a success, the effect ends. On a failure, the creature is petrified until freed by the greater restoration spell or other magic.
6. Death Ray. The targeted creature must succeed on a DC 19 Dexterity saving throw or take 55 (10d10) necrotic damage. The target dies if the ray reduces it to 0 hit points.

Create Sustenance. The aberrant mind magically creates enough sustenance to sustain itself for 24 hours.

Mind Blast (Recharge 5–6). The aberrant mind magically emits psychic energy in a 60-foot cone. Each creature in that area must succeed on a DC 19 Intelligence saving throw or take 33 (6d10) 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.

Enslave (3/Day). The aberrant mind targets one creature it can see within 30 feet of it. The target must succeed on a DC 19 Wisdom saving throw or be magically charmed by the aberrant mind until the aberrant mind dies or until it is on a different plane of existence from the target. The charmed target is under the aberrant mind's control and can't take reactions, and the aberrant mind and the target can communicate telepathically with each other over any distance.

Whenever the charmed target takes damage, the target can repeat the saving throw. On a success, the effect ends. No more than once every 24 hours, the target can also repeat the saving throw when it is at least 1 mile away from the aberrant mind.

Spell Reflection. If the aberrant mind makes a successful saving throw against a spell, or a spell attack misses it, the aberrant mind can choose another creature (including the spellcaster) it can see within 30 feet of it. The spell targets the chosen creature instead of the aberrant mind. If the spell forced a saving throw, the chosen creature makes its own save. If the spell was an attack, the attack roll is rerolled against the chosen creature.

The aberrant mind 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 aberrant mind regains spent legendary actions at the start of its turn.

Cantrip. The aberrant mind casts a cantrip.

Detect. The aberrant mind makes a Wisdom (perception) check.

Eye Ray. The aberrant mind uses one random eye ray.

Lesser Spell (Costs 2 Actions). The aberrant mind casts a spell of 3rd level or lower. 

If the aberrant mind's psychic resilience trait has activated in the last hour, it can use the options below as legendary actions.

 Tentacles. The aberrant mind makes one tentacle attack

Psychic Leech (Costs 2 Actions). One creature charmed by the aberrant mind takes 14 (4d6) psychic damage, and the aberrant mind regains hit points equal to the damage the creature takes.

Greater Spell (Costs 3 Actions). The aberrant mind casts a spell of 4th level or higher.

Mind Blast (Costs 3 Actions). The aberrant mind recharges its Mind Blast and uses it.