Arbiter

Eldritch Nature. The Arbiter doesn't require air, food other than memories, drink, or sleep.

Devouring Telepathy. If a creature communicates telepathically with the arbiter, the arbiter may attempt to consume one of the target's memories. The target must succeed a DC 27 Charisma saving throw or take 47 Psychic damage and become Incapacitated until the end of it's next turn, and the range of the Arbiter's telepathy increases by 10 feet for the same duration. Additionally, whenever the arbiter kills a creature, the range of its telepathy increases by 10 feet until the end of it's next turn or until it takes Force damage.

 Administrative Presence. Creatures other than arbiters within range of the arbiter's telepathy have vulnerability to Psychic and Lightning damage and resistance to Force damage. Additionally, any creature from whom the arbiter has devoured a memory must make a DC 27 Charisma saving throw or take 13 Psychic damage whenever it starts or ends it's turn within range of the arbiter's telepathy.

Multiattack. The arbiter makes three tentacle attacks.

Tentacle. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 13 (3d6 + 3) piercing damage. If the target is a creature, it must succeed on a DC 16 Constitution saving throw or take 9 Poison damage and become Poisoned until the end of it's next turn. While Poisoned in this way, the creature has vulnerability to Psychic and Lightning damage. Additionally, once the creature takes Lightning damage, it cannot take reactions until the Poisoned condition ends for it.

Zombify(3/Day). The Arbiter reanimates the corpse of a humanoid within the range of the arbiter's telepathy. To be reanimated, the creature must have died from Lightning, Poison or Psychic damage, and there must not be a sentient creature other than an arbiter who can remember the creature's name. The corpse becomes a Zombie under the Arbiter's control. The zombie has vulnerability to Force damage and resistance to Lightning, Psychic and Cold damage, and anything the zombie senses, the arbiter also senses. The arbiter can also take direct control of any zombie under it's control. While the arbiter is directly controlling a zombie, the arbiter has telepathy out to 10 feet of the zombie.

Innate Spellcasting. The arbiter casts one of the following spells, requiring no material components and using Intelligence as the spellcasting ability. When the arbiter casts Modify Memory, it can only target a creature within range of it's telepathy, and when it casts Ray of Frost if can choose to deal Acid, Poison, or Psychic damage instead of Cold (Spell Save DC 20, spell attack modifier +10):                                                   At Will: Shocking Grasp, Mind Sliver, Modify Memory, Ray of Frost   3/day each: Lightning Bolt, Hunger of Hadar, Animate Dead   1/day: Weird, Call Lightning, Silent Image

Haunting Phantom. The arbiter chooses a creature within range of its telepathy, or a creature from whom it has stolen a memory. The creature must make a DC 16 Wisdom saving throw or take 3 Psychic damage and be Charmed by the arbiter until it takes damage other than Psychic or a creature casts a spell that cures a disease or breaks a curse on the creature. While Charmed in this way, the creature cannot see or hear the arbiter, and believes that a dead loved one is communicating with them when the arbiter makes telepathic contact with the them.

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

Corrosive Tentacle. The arbiter makes one tentacle attack. If the attack hits, the target must make a DC 16 Constitution saving throw or take an additional 13 Acid damage

Psychic Drain (Costs 2 Actions). One creature Charmed by the arbiter takes 10 (3d6) psychic damage, and the arbiter regains hit points equal to the damage the creature takes. Additionally, the range of the arbiter's telepathy increases by 5 feet until the end of the arbiter's next turn.