Beetlejuice

Born-Dead. BJ does not require breathing, eating, drinking, or sleep (unless Exhausted).

Rejuvenation. If destroyed or killed, BJ regenerates in 1d12 days. He regains all hit points and spell slots, but suffers from 4 levels of Exhaustion until finishing a long rest.

Spellcasting. Spell save DC 19, +11 to hit with spell attacks.
At-Will Spells. Alter Self, Detect Magic, Detect Poison and Disease, Identify, Misty Step, Speak with Dead
Cantrips. Chill Touch, Control Flames, Create Bonfire, Fire Bolt, Infestation, Prestidigitation, Vicious Mockery
1st level (4 slots). Burning Hands, Chaos Bolt, Dissonant Whispers, Hellish Rebuke, Ray of Sickness
2nd level (4 slots). Hold Person, Pyrotechnics, Silence
3rd level (3 slots). Animate Dead, Counterspell, Fear, Remove Curse, Tiny Hut
4th level (3 slots). Black Tentacles, Blight, Phantasmal Killer, Wall of Fire
5th level (2 slots). Immolation, Insect Plague, Negative Energy Flood
6th level (2 slots). Circle of Death, Disintegrate, Eyebite, Irresistible Dance
7th level (2 slots). Finger of Death, Fire Storm, Power Word Pain, Resurrection, Teleport
8th level (1 slot). Maddening Darkness, Reality Break
9th level (1 slot). Time Stop, Weird

Curse of Etherealness. Bestowed by his mother for trying to befriend living creatures, BJ has been banished to the Ethereal Plane.

Curse Loophole. When another creatures utters BJ's name--three times, spoken, unbroken--he is summoned to an unoccupied space within 15 ft. of the creature, and the curse is lifted.

Curse Loophole Addendum. If summoned in an outside space, the curse can only be lifted for up to 24 hours at a time; if BJ uses magic, the time freed is reduced by the number of hours equal to the spells' casting levels. Curse can be reinstated by saying BJ's name three more times. If this occurs, BJ is drained of all spell slots, and suffers 4 levels of exhaustion; if summoned indoors, BJ can use magic as normal, but cannot leave--or destroy--the enclosed space (i.e. house, dungeon, etc.) without Exhaustion or losing spell slots. Exhaustion ends after a long rest. Spell slots are returned after 1d4 days. These additional penalties are not added if 24-hour timer runs out.

(Yet Another) Curse Loophole. Any undead, or creatures with True Sight, can see BJ while the Curse is active. Occasionally, there are others who have been able to see him, but the cause of this is unknown.

Possession (1/Day). One undead creature that BJ can see within 15 feet must succeed on DC 16 Charisma saving throw or be possessed by him; he then disappears, and the target is incapacitated and loses control of its body. BJ now controls the body but doesn't deprive the target of awareness (if it has any). BJ can't be targeted by any attack, spell, or other effect, except ones that turn undead, and he retains his alignment, Intelligence, Wisdom, Charisma, and immunity to being charmed. He otherwise uses the possessed target's statistics, but doesn't gain access to the target's knowledge, class features, or proficiencies. The possession lasts until the body drops to 0 hit points, BJ ends it as a bonus action, or he is turned or forced out by an effect like the dispel evil and good spell. When the possession ends, BJ reappears in an unoccupied space within 5 feet of the body. The target is immune to BJ's Possession for 24 hours after succeeding on the saving throw or after the possession ends.

Misty Step. Briefly surrounded by silvery mist, he can teleport up to 30 feet to an unoccupied space that he can see.

Hellish Rebuke. He snaps his fingers, and the creature that damaged him is momentarily surrounded by hellish flames. The creature must make a Dexterity saving throw. It takes 2d10 fire damage on a failed save, or half as much damage on a successful one.
At Higher Levels: When one casts this spell using a spell slot of 2nd level or higher, the damage increases by 1d10 for each slot level above 1st.

Legendary Resistance (3/Day). If BJ fails a saving throw, he can choose to succeed instead.

BJ 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. BJ regains spent legendary actions at the start of his turn.

Cantrip (costs 1 action) Casts a Cantrip.

Grim Reaper's Sprint (costs 2 actions) Moves up to his speed and makes one melee or spell attack.

Teleport (costs 2 actions) The creature magically teleports, along with any equipment it is wearing or carrying, up to 120 feet to an unoccupied space it can see.

Frightening Gaze (costs 2 actions) The creature fixes its gaze on one creature it can see within 10 feet of it. The target must succeed on a DC 18 Wisdom saving throw against this magic or become frightened for 1 minute. The frightened target can repeat the saving throw at the end of each of its turns, 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 the creature’s gaze for the next 24 hours.