Azrei Oceanbreath

Amorphous. Azrei can move through a space as narrow as 1 inch wide without squeezing.

Aversion to Fire. If the Azrei takes fire damage, it has disadvantage on attack rolls and ability checks until the end of its next turn.

Multiattack. Azrei makes two pseudopod attacks, a Cantrip, and uses Eat Memories. 

Pseudopod. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 11 (3d6 + 4) bludgeoning damage plus 7 (2d6) psychic damage.

Eat Memories. The Azrei targets one creature it can see within 5 feet of her. The target must succeed on a DC 18 Wisdom saving throw or take 44 (8d10) psychic damage and become memory drained until it finishes a short or long rest or until it benefits from the greater restoration or heal spell. Constructs, oozes, plants, and undead succeed on the save automatically.

While memory drained, the target must roll a d4 and subtract the number rolled from any ability check or attack roll it makes. Each time the target is memory drained beyond the first, the die size increases by one: the d4 becomes a d6, the d6 becomes a d8, and so on until the die becomes a d20, at which point the target becomes unconscious for 1 hour. The effect then ends.

When Azrei causes a target to become memory drained, she learns all the languages the target knows and gains all its proficiencies, except for any saving throw proficiencies. 

Innate Spellcasting. The Azrei's innate spellcasting ability is Intelligence (spell save DC 17). She can innately cast the following spells, requiring no material components:

At will: charm person (as 5th-level spell), detect thoughts, hold person, Alter Self (can become a Medium Humanoid when changing her appearance)

3/day each: confusion, dimension door, dominate person, fear, hallucinatory terrain, hold monster, hypnotic pattern, telekinesis

Wizard Spellcasting. The Azrei is a 11th-level spellcaster. Her spellcasting ability is Intelligence (spell save DC 18, +9 to hit with spell attacks). Azrei has the following Wizard spells prepared:

Ritual (at will; + 10 extra minutes of casting time): detect magic, floating disk, sending, arcane eye

Cantrips (at will): lightning lure, shocking grasp, infestation, Mage Hand, light,  prestidigitation

1st level (4 slots): Absorb Elements, burning hands, Sleep, feather fall

2nd level (3 slots): invisibility, Darkness, Misty step, Scorching Ray, suggestion, knock

3rd level (3 slots): tidal wave, Fly, counterspell, dispel magic, summon lesser demons

4th level (3 slots): vitriolic sphere, dimension door, resilient sphere, mordenkainen's private sanctum

5th level (2 slots): Dawn, Mislead, scrying

Sulfurous Impersonation. As a bonus action, Azrei can extrude a piece of itself that assumes the appearance of one Medium or smaller creature whose memories it has stolen. This simulacrum appears, feels, and sounds exactly like the creature it impersonates, though it smells faintly of sulfur. Azrei can impersonate 2d6 + 1 different creatures, each one tethered to its body by a strand of slime that can extend up to 120 feet away. For all practical purposes, the simulacrum is Azrei, meaning she occupies her current space and the simulacrum’s space simultaneously. The slimy tether is immune to damage, but it is severed if there is no opening at least 1 inch wide between the Azrei’s main body and the simulacrum. The simulacrum disappears if the tether is severed.

Azrei 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 Azrei regains spent legendary actions at the start of its turn.

Detect. The Azrei makes a Wisdom (Perception), (Insight) or Intelligence (Arcana) check.

Cantrip (Costs 2 Actions). Azrei casts one cantrip.

Cast a Spell (Costs 3 Actions). The Azrei casts a spell from its list of prepared spells,  expend a spell slot as normal.