Inescapable Death. The Grim Reaper's reaping scythe attack bypasses immunity or resistance to necrotic damage.

Legendary Resistance (3/Day). When the Grim Reaper fails a saving throw it can choose to succeed instead.

Slowing Aura. Any creature that starts its turn within 15 ft. of the Grim Reaper must succeed on a DC 27 Wisdom saving throw. If they fail, their speed is halved until the start of their next turn.

Multiattack. The Grim Reaper makes two Reaping Scythe attacks and a Weakening Ray attack.

Reaping Scythe. Melee Weapon Attack: +19 to hit, reach 10 ft., all targets within reach. Hit: 46 (8d8 + 10) necrotic damage. 

Weakening Ray. The Grim Reaper shoots a beam of gray light at a creature it can see within 120 ft. of it. The target must succeed a DC 27 Constitution saving throw or deal half damage with all of its attacks until the end of its next turn.

Absorb Soul. The Grim Reaper targets a lost soul it can see within 60 ft. of itself. The lost soul is reduced to 0 hit points and disappears, and the Grim Reaper regains 10 hit points.

Shadow Form. When the Grim Reaper is hit by an attack, it can use its reaction to temporarily fade into shadows. It takes half damage from all attacks except attacks that deal radiant damage until the start of its next turn.

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

Conjure Souls (Costs 2 Actions). The Grim Reaper summons 1d6 lost souls (Use the wraith stat block). The lost souls last for one minute or until they are reduced to 0 hit points.

Grab Soul. The Grim Reaper targets a living creature it can see within 60 ft. of itself. The target must succeed a DC 27 Wisdom saving throw or be paralyzed until the end of their next turn.