Aspect of The Ceaseless Hunger

Gravity well. all creatures within 15 feet have their speed halved

Sheer Nihility. all creatures within 150 feet have their damage reduced to 1 damage every single attack. 

Incomprehensible. The main body of the creature cannot be attacked, only its tentacles which split its health bar, 6 health each. 

Tentacles. all 4 tentacles take an action on the turn of the Aspect of The Ceaseless Hunger

Tentacle swing. Melee Weapon Attack: +10 to hit, reach 5 ft, hits all enemy targets in its radius Hit:  18 (2d8 necrotic damage, 1d8 force damage +5)

Hungered beam. RangedWeapon Attack: +6 to hit, range 70/140 ft., 1 target. Hit:  20 (2d10 Necrotic damage, 1d6 force damage +6)

Blight(recharge 3 turns). Casts the Blight spell at 4th level on one target. The target much make a dc 15 con save or take 8d8 necrotic damage on a failed save, or half as much damage on a successful one.

Draining beam(recharge 2 turns). ranged weapon attack: +1 to hit, range 30/60 ft, 1 target. hit: 10(1d10 force damage +5), target loses one second or first level spell slot

Aspect of The Ceaseless Hunger has 9 legendary actions per day, and gets 3 back per turn 

Legendary Resistance(costs 2 actions). Aspect of The Ceaseless Hunger can resist any effect or spell if they fail its check. 

Hungers light(costs 1 action). casts moonbeam at 1st level not requiring concentration on any spot it can see for 2 turns. casting it while its active changes location and resets duration. 

Teleportation(2 actions). teleport up to 30 feet away from its current location. 

Heal tentacle(3 actions 1 turn cooldown). heal one tentacle 2 health.