Aspect of Oberon

Divine Awareness. Oberon knows if he hears a lie.

Ethereal Jaunt. As a bonus action, Oberon can magically shift from the Material Plane to the Ethereal Plane, or vice versa.

Hellish Rejuvenation. If Oberon is slain, his body is destroyed but his soul refuses it's fate, returning to his domain in the Nine Hells as a disembodied spirit fashioning a new body for itself in 1d4 years. When the new body is complete, Oberon regains all his hit points and becomes active again.

Legendary Resistance (5/Day). If Oberon fails a saving throw, he can choose to succeed instead.

Innate Spellcasting. Aspect of Oberon's innate spellcating ability is Charisma (spell save DC 26, +18 to hit with spell attacks). Oberon can cast the following spells, requiring no material components:

At will: zone of truth, animate dead (as an action), command, spirit guardians (necrotic damage only), speak with dead

3/day each: infernal calling (as an action), contagion, cloudkill (as a 6th level spell), circle of death, soul cage

1/day each: finger of death, time ravage, power word kill, tether essence, magic jar

Special Equipment. Oberon carries a magical scythe named Scythe of the Damned. It is a +3 scythe.

Unusual Nature. Oberon doesn't require air, food, drink or sleep. In addition, as long as Abraxas is alive, Oberon does not age and cannot be aged magically.

Multiattack. Oberon uses his Frightful Presence, or Steal Soul (if available), he then makes two attacks with Scythe of the Damned. He can use Constrict in place of a scythe attack.

Constrict. Melee Weapon Attack: +17 to hit, reach 15 ft., one target. Hit: 25 (3d10 + 9) bludgeoning damage and the target is grappled (escape DC 23). Until the grapple ends the target is restrained and Oberon cannot constrict another creature.

Scythe of the Damned. Melee Weapon Attack: +20 to hit, reach 10 ft., one target. Hit: 24 (3d8 + 11) slashing damage plus 38 (7d10) necrotic damage and the target can't regain hit points until the start of its next turn. A target reduced to 0 hit points by this attack dies.

Flying Scythe. Oberon releases his scythe to hover magically in an unoccupied space within 5 feet of him. If he can see the scythe, he can mentally command it as a bonus action to fly up to 50 feet and either make one attack against a target or return to Oberon's hands. If the hovering scythe is targeted by any effect, Oberon is considered to be holding it. The hovering scythe falls if he dies.

Frightful Presence. Each creature of Oberon's choice that is within 120 feet of Oberon and aware of him must succeed on a DC 26 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature’s saving throw is successful or the effect ends for it, the creature is immune to Oberon’s Frightful Presence for the next 24 hours.

Soul Syphon (Recharge 5-6). Oberon points his open palm at a target he can see within 10 feet of him and forces them to make a DC 25 Constitution saving throw. On a failed save their soul leaves their body and becomes trapped within Oberon, until he is destroyed or chooses to release it as a bonus action. The body of the target drops whatever it was holding and falls incapacitated. On a success the target takes 54 (12d8) necrotic damage and Oberon heals for half the damage done. If the damage reduces the target to 0 hit points their soul is trapped as if they failed the saving throw. Oberon gains 30 temporary hit points each time he traps a soul in this way. 

If Oberon drops to 0 hit points, any soul he had trapped is released returning back into its body. If the body is no longer in livable conditions it turns into a specter.

Aspect of Oberon 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. Aspect of Oberon regains spent legendary actions at the start of its turn.

Scythe of the Damned. Oberon makes one Scythe of the Damned attack.

Channel Negative Energy (Costs 2 Actions). Oberon magically unleashes negative energy. Creatures within 60 feet of him, including ones behind barriers and around corners, can't regain hit points until the end of Oberon's next turn.

Disrupt Life (Costs 3 Actions). Each non-undead creature within 20 feet of Oberon must make a DC 25 Constitution saving throw against this magic, taking 66 (12d10) necrotic damage on a failed save, or half as much damage on a successful one.