Azathoth The Unliving

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

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

At will: detect thoughts, levitate

1/day each: dominate monster, plane shift (self only)

Spellcasting. The alhoon is a 12th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 17, +9 to hit with spell attacks). The alhoon has the following wizard spells prepared:

Cantrips (at will): chill touch, dancing lights, mage hand, prestidigitation, shocking grasp

1st level (4 slots):Absorb Elements, disguise self, magic missile, shield

2nd level (3 slots): invisibility, mirror image, misty step

3rd level (3 slots): counterspell, sleet storm, lightning bolt

4th level (3 slots): Dimention Door, Evard's black tentacles, Otiluke's Resilient Sphere

5th level (2 slots): Synaptic Static, wall of force

6th level (1 slot): disintegrate, Mass Suggestion

Turn Resistance. The Alhoon has advantage on saving throws against any effect that turns undead.

Necromantic Revitalization. If Azathoth is killed he regenerates within 1d10 days in his lair

Wand Of Orcus:

Regeneration. The Alhoon regains 1d6 hit points at the start of its turn if he has at least 1 hit point.

Artifact Dependence: The Alhoon is blinded when it is greater that 10 feet away from the wand of Orcus. It also must eat 6 times as many brains as it normally does

Aura of death: Creatures with challenge rating zero as well as plants that aren't creatures drop to 0 hitpoints while within 10 ft of the Wand of Orcus

Spells. The wand has 7 charges. While holding it, Azathoth can use an action and expend 1 or more of its charges to cast one of the following spells (save DC 18) from it: animate dead (1 charge), blight (2 charges), circle of death (3 charges), finger of death(3 charges), power word kill (4 charges), or speak with dead (1 charge). The wand regains 1d4 + 3 expended charges daily at dawn.

Chilling Grasp. Melee Spell Attack: +9 to hit, reach 5 ft., one target. Hit: 10 (3d6) cold damage.

Wand of Orcus. Melee Weapon Attack: +8 to hit, reach 5 feet., one target. Hit 6 (1d6 +3) Magic Bludgeoning Damage. Plus 7 (2d12) Necrotic Damage. 

Mind Blast (Recharge 5-6). The alhoon magically emits psychic energy in a 60-foot cone. Each creature in that area must succeed on a DC 17 Intelligence saving throw or take 27 (5d8+4) psychic damage and be stunned for 1 minute. A target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Shield. cast the shield spell. 

Absorb Elements.  cast absorb elements. 

Counterspell. cast counterspell. 

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

Tentacles. The Alhoon makes one attack with its tentacles.

Extract Brain (Costs 2 Actions). The Alhoon uses Extract Brain.

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

Cast Spell (Costs 1–3 Actions). The Allhoon uses a spell slot to cast a 1st-, 2nd-, or 3rd-level spell that it has prepared. Doing so costs 1 legendary action per level of the spell.

When Azathoth Drops to 0 hitpoints he instead regains 105 hitpoints and gains 6d10 Temporary hitpoints as his body is animated by the nefarious power of Orcus.

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

Soul Shield (Costs 1 Action).  Azathoth Gains 3d10 Temporary Hotpoint's.  

Shriek of Madness (Costs 2 Actions).  Azathoth lets out a howl of teror up to 3 creatures it chooses that can hear it within 60 ft must make a DC 17 wisdom save or become frightened.  

Fiends in Low Places (Costs 3 Actions). Azathoth brings fourth 1d4 deamons of Cr 2 or lower they roll their own initiative and when each of them is killed Azathoth regains 2d10 Hitpoints.