Homebrew
Legendary Resistance (3/Day). If the Desolation Reaper fails a saving throw, it can choose to succeed instead. Magic Resistance. The Desolation Reaper has advantage on saving throws against spells and other magical effects. Turn Immunity. The Desolation Reaper is immune to all effects that turn or dominate undead. Assassination. Any creature the Desolation Reaper strikes with advantage must succeed on a DC 15 Constitution saving throw or suffer double damage from the attack. Regeneration. The Desolation Reaper regains 10 hit points at the start of its turn. If the Desolation Reaper takes radiant damage, this trait doesn't function at the start of its next turn. Incorporeal Movement. The Desolation Reaper can move through other creatures and objects as if they were difficult terrain. It takes 6 1d10 force damage if it ends its turn inside an object. Ethereal Sight. The Desolation Reaper can see 120 feet into the Ethereal Plane when it is on a mortal plane, and vice versa. Soul Reaver. The soul of a creature brought to 0 hit points by the Desolation Reaper is immediately annihilated. A creature slain this way can only be brought back by divine intervention. No Escape. If a creature's soul evades death at the hands of the Desolation Reaper by retreating elsewhere (such as through the clone spell), it immediately knows where it has gone, even if it is on a different plane of existence. Undead Nature. The Desolation Reaper does not need to eat, drink, breathe, or sleep. Deathless Servants. If the Desolation Reaper is reduced to 0 hit points, it rematerializes on the Ethereal Plane immediately. If it was killed by its intended target, a free-willed Reaper is called to hunt the target. Otherwise, it uses its Chase bonus action to immediately continue the hunt.
Multiattack. The Desolation Reaper can use its Horrifying Visage. It then makes two Ethereal Scythe attacks, though it can substitute one with its Necrotic Blast. Ethereal Scythe. Melee Weapon Attack: +11 to hit, range 5 ft., one target. Hit: 17 3d6+6 necrotic damage. The target must succeed on a DC 16 Constitution saving throw or take 1d6 Constitution damage. This damage lasts until the target finishes a long rest. The target dies if its Constitution reaches 0. Necrotic Blast. Ranged Spell Attack: +11 to hit, range 120 ft., one target. Hit: 15 2d8+6 necrotic damage. The target must succeed on a DC 14 Wisdom saving throw or become paralyzed for 1d4+4 rounds. Horrifying Visage. Each non-undead creature within 90 feet of the Desolation Reaper that can see it must succeed on a DC 16 Wisdom saving throw or be frightened for 1 minute. A frightened target can repeat the saving throw at the end of each of its turns, with disadvantage if the Desolation Reaper is within line of sight, 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 that particular Desolation Reaper’s Horrifying Visage for the next 24 hours. Plane Shift. The Desolation Reaper may transport between the various mortal planes of existence and the Ethereal Plane (or any demiplane therein) at will. It does not have the power to bring the living with it. While in the Ethereal Plane, it can neither affect nor be affected by creatures on any other plane.
Invisibility (Recharge 6). The Desolation Reaper becomes invisible as per Invisibility. Chase. The Desolation Reaper transports beyond any barrier to appear 5 feet from its quarry. Planar barriers, magic circles, teleportation inhibitors, and other defenses against such teleportation are completely ignored by this action.
Solidarity. When the Desolation Reaper has an attack made against it by a creature other than its quarry, it conjures an Aegis Reaper to attack the creature that attacked it. This Aegis Reaper pursues and attacks this singular creature to the best of its ability. This Aegis Reaper is not a true Reaper and vanishes either upon its master's death or its master's culling of its targeted soul. Unless the target it was set upon is also slated for death, the soul is not taken and upon this Aegis Reaper's vanishing, the creature is brought back to life with 1 hit point.
The Desolation 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 Desolation Reaper regains spent legendary actions at the start of his turn.