Oath of the Reaper

While many Paladins serve a deity, there are others who serve an energy, a balance. Among these are an ancient order or paladins all but extinct now; except for a handful of strangers from all walks of life. Reapers are a familiar concept, reaping the life of a creature and ushering them to their final destination. While this concept exists, any knowledge of such a creature has never been seen. A primordial force, with origins beyond time itself, has need of a mortal. Paladins may be the target of this and be asked to fulfill a particular duty; swearing an Oath of the Reaper. 

Channel Divinity: Life After Death

Starting at 3rd level:

The Reaper can activate its tether to the Primordial gathering strength from the recently departed. The Reaper regains hit points or every creature killed within the past hour inside of a 30 ft cone.

Marked for Death

Starting at 7th level:

The Reaper marks an enemy creature within 30 ft that is no more than one size category large than itself and marks it for death. The reaper then pulls that enemy up to 30 ft towards it and makes a melee weapon attack at advantage. For 1 minute, at the end of the creatures turn, it can make a charisma save against the reaper's spell DC in an attempt to break free of the magical hold. All attacks made against the targeted creature by the reaper or its allies are made with advantage while it is under the effects of this ability. If the reaper takes damage at any point during the ability's 1 minute duration, the following charisma saving throw that the marked creature makes is with advantage. The reaper cannot move while this ability is active and it can dismiss this action at any time.

Mass Departure

Starting at level 15:

The reaper hastens as many foes as it can to their death with each strike. Every time the Reaper strikes a target, surrounding enemies within 10 ft of the target receive 25% of the total damage done to the original target. This effect does not divide the original damage among its allies, rather it deals 100% damage to the original, and 25% of that damage to surrounding enemies as well.

Soul Curse

At level 20:

The reaper channels the energy of the death directly into the soul of a single creature that it can see. Primordial death demands that this creature die. Once per long rest, the reaper curses the soul of the creature forcing it to succeed on a Charisma saving throw. On a failure, the creature loses 5% of its maximum hit point at the start of its turn for the 1 minute duration. While this ability is not a traditional spell, it is still requires spell concentration and follows the rules of it.