Aspect of Death

Incorporeal Movement. Aspect of Death can move through other creatures and objects as if they were difficult terrain.

Cantrips (at will): greater invisibility 

Lingering Spite. When the Aspect of Death is reduced to 0 hit points, it's incorporeal form explodes in a burst of necrotic energy. Each creature within 15 feet of it must make a DC 16 Constitution saving throw, taking 14 (8d6) necrotic damage on a failed save, or half as much damage on a successful one.

Legendary Resistance (4/Day). If the Aspect fails a saving throw, it can choose to succeed instead.

Uncanny Tracker. The Aspect can unerringly track any creature it has wounded, and it knows the distance and direction to its quarry as long as the two of them are on the same plane of existence.

Multiattack. Aspect of Death makes two attacks with it's Curtain-Call Scythe or one attack with rotten fate

Curtain-Call Scythe. Melee Weapon Attack: +14 to hit, reach 10 ft., one creature. Hit: 18 (2d10 + 7) slashing damage plus 19 (6d12) necrotic damage. Any creature reduced to 0 hit points by this attack dies, with its body and everything it is wearing and carrying, except magic items, exploding into a cloud of ash. The creature can be restored to life only by means of a wish spell..

Rotten Fate. The Aspect of Death causes necrotic magic to engulf one creature it can see within 120 feet of itself. The target must make a DC 22 Constitution saving throw, taking 96 (8d8 + 60) necrotic damage on a failed save, or half as much damage on a successful one. A Humanoid killed by this magic rises as a shadow (see the Monster Manual) at the start of the Aspect’s next turn and acts immediately after the Aspect of death in the initiative order. The shadow is under the Aspect’s control.

Frightening Gaze. The Aspect  fixes it's gaze on one creature it can see within 10 feet of it. The target must succeed on a DC 17 Wisdom saving throw against this magic or become frightened for 1 minute. The frightened target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a target's saving throw is successful or the effect ends for it, the target is immune to the Aspect’s gaze for the next 24 hours.

The Aspect of Death moves up to half it's flying speed without provoking opportunity attacks. When it passes within 15 feet of a creature during this move, that creature must succeed on a DC 22 Dexterity saving throw or take 11 (2d10) necrotic damage. A creature can take this damage no more than once during the move.