Cruaver, the Consuming Void

Singularity Aura. A 60-foot aura of gravitational distortion surrounds Cruaver. Ranged attacks targeting him have disadvantage, and teleportation into or out of the area requires a DC 24 Intelligence save except for Cruaver who can teleport anywhere inside the field with his movement.

Living Event Horizon. When a creature within 30 feet of Cruaver casts a spell, it must make a DC 24 Wisdom saving throw or the spell is consumed by void energy (no effect, spell slot lost). Once per round.

Multiattack. Cruaver makes three attacks: one with Void Maw and two with Claws of Collapse.

Void Maw. Melee Weapon Attack: +17 to hit, reach 10 ft., one target.
Hit: 36 (5d10 + 9) force damage. The target must succeed on a DC 24 Constitution save or suffer Void Fracture (disadvantage on Strength saves and half movement for 1 minute).

Claws of Collapse. Melee Weapon Attack: +17 to hit, reach 5 ft., one target.
Hit: 27 (4d8 + 9) slashing damage + 13 (3d8) force damage.

Annihilation Pulse (Recharge 5–6). Cruaver emits a wave of vacuum force in a 90-foot cone. Each creature in the area must make a DC 24 Constitution save, taking 90 (20d8) force damage on a failed save, or half as much on a success. Creatures reduced to 0 HP by this effect are disintegrated, leaving behind only void dust.

Black Prism (1/Day). Cruaver folds light into a singular point. Choose 3 creatures. They must each succeed on a DC 24 Charisma save or be trapped in a crystal of null-light for 1 minute (incapacitated, blind, and silenced). Each turn they may reroll the save at the end of their turn.

Voidflame Breath (Recharge 5–6).Cruaver exhales a sweeping torrent of writhing voidfire in a 120-foot line that is 20 feet wide. The attack distorts light and crushes sound, leaving only overwhelming silence and disintegration in its wake. Each creature in the area must make a DC 24 Dexterity saving throw, taking: 96 (16d10) force damage plus 96 (16d10) necrotic damage on a failed save, or half as much on a successful one.

Aftereffects:
The affected area becomes nullspace for 1 minute:

Magical light is extinguished.
The area becomes difficult terrain.
Any creature that starts its turn in the area takes 10 (3d6) force damage and cannot regain hit points until it leaves the zone.

Gravity Lash (3/Day). As a reaction to being hit, Cruaver lashes out with tendrils of collapsed space. The attacker must succeed on a DC 24 Strength save or be restrained by gravitational bindings (escape DC 24).

Cruaver can take 3 legendary actions, choosing from the options below.

• Voidlash. Make one Claw of Collapse attack.

• Gravity Well (Costs 2 Actions). Pull all creatures within 60 feet 15 feet closer. DC 24 Strength save to resist.

• Phase Warp (Costs 2 Actions). Cruaver vanishes and reappears anywhere within 120 feet.

• Graviton Shear (Costs 3 Actions). A line 100 feet long and 10 feet wide explodes with gravitational collapse. Creatures in the line must make a DC 24 Dexterity save or take 55 (10d10) force damage and be flung 30 feet.

When Cruaver is reduced to 0 hit points, he does not fall unconscious. Instead, he releases a pulse of pure void and force energy. His hit points return to 300, all conditions affecting him end, and reality begins to warp around him.

For the rest of the encounter:

• All attacks deal an additional 2d12 force damage.

• Cruaver can take two turns per round, one on his initiative and one at initiative count 10.

• The battlefield is treated as his Lair regardless of location.