Awoken

Wellspring of the Deep. If a creature casts detect thoughts while within range of an awoken, the caster must make a DC 18 Intelligence saving throw or suffer 44 (8d10) psychic damage and suffers from temporary insanity. On a success, the caster takes half damage and does not go insane.

Unsettling Aura. When a creature begins their turn or moves within 15 feet of the awoken, they must succeed on a DC 18 Wisdom saving throw or move directly to a point at least 20 feet away from the awoken.

Infinite Consciousness. This creature automatically succeeds on saving throws against enchantment spells. This creature never needs to sleep, and cannot be put to sleep by any means. This creature is always aware of the presence of sentient creatures within 30 feet.

Spellcasting. The awoken is a 9th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 18, +10 to hit with spell attacks). It has following spells prepared:
Cantrips (at will): Eldritch Blast, Mage Hand, Minor Illusion

1st level (4 slots): Fog Cloud, Hex, Shield

2nd level (3 slots): Invisibility, Misty Step, 

3rd level (3 slots): Hunger of Hadar, Slow

4th level (3 slots): Evard's Black Tentacles, Confusion

5th level (1 slot): Telekinesis

Ascendant Step. The awoken can cast Levitate on itself at will

Agonizing Blast. The awoken adds its Intelligence modifier to the damage it deals with Eldritch Blast.

Multiattack. The awoken makes two attacks with its tentacles, or two eldritch blasts.

Tentacle. Melee Unarmed Attack: +6 to hit, reach 10 ft., 1 target. Hit: 7 (1d10 + 2) bludgeoning damage and 9 (2d8) psychic damage. 

Eldritch Blast. Ranged Spell Attack: +10 to hit, range 120 ft., one creature. Hit: 11 (1d10+6) force damage.

Reveal Thy True Form. (Recharge 5-6) The awoken sheds its physical facade, revealing the writhing horrors its body is a conduit for. Every creature that can see the awoken must succeed on a DC 18 Wisdom saving throw or be frightened for 1 minute. If a creature fails this save by 5 or more, they are stunned for this duration. Creatures affected by these conditions can repeat the saving throw at the end of their turns, ending them on success. If a creature fails this save by 10 or more, they immediately fall Unconscious and another creature must use an action to wake them.

The Awoken can take 2 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 Awoken regains spent legendary actions at the start of its turn.

Cantrip The Awoken casts a cantrip. 

Spell (Costs 2 Actions) The Awoken Casts a spell.