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

Undying. If Xowie is slain, his soul refuses to accept its fate and lives on as a disembodied spirit that fashions a new body for itself after 1d100 years. Xowie's soul can fashion a new body even if its old body was burned to ash or otherwise obliterated. When the new body is complete, Xowie regains all his hit points and becomes active again. Xowie's new body appears anywhere within 100 miles of where Xowie was slain.

Unusual Nature. Xowie doesn’t require air, food, drink, or sleep.

Better Than You. Xowie can concentrate on two spells at once and rolls concentration checks separately.

Multiattack. Xowie makes one attack with his Chill Touch and then Casts a Spell.

Chill Touch: Spellcasting attack: +9 to hit, reach 5 ft., one target. Hit: 18 (4d8) necrotic damage. The target can't regain hit points until the start of Xowie's next turn. If he hits with this attack, he can make another one as a bonus action.

Spellcasting. Xowie is a 20th level spellcaster with the following spells suggested. He has access to all knowable wizard spells. He has a +11 to hit and a spell save DC of 19.

At will: Lightning Bolt, Dispel Magic, Spray of Cards, Vortex Warp, Enlarge/Reduce though it only lasts until the end of their next turn

4/day: Polymorph, Telekinesis, Antagonize

3/day: Otto's Irresistible Dance, Eyebite, Power Word Pain

1/day: Power Word Stun

1/day: Power Word Kill

Goatmancer. Once per day, Xowie can summon 2d4 fiendish goats to aid him in battle. These goats have the same statistics as a regular goat, except they are under Xowie's control and have a maximum hit point of 10. As a bonus action, he can resurrect one of the goats if they fall.

At will spellcasting. Xowie can cast Ashardalon's Stride at will. 

Dread Counterspell (5/day). Xowiea utters a dread word to interrupt a creature he can see that is casting a spell. If the spell is 4th level or lower, it fails and has no effect. If the spell is 5th level or higher, Xowie makes an Intelligence check (DC 10 + the spell’s level). On a success, the spell fails and has no effect. Whatever the spell’s level, the caster takes 6 (2d6) psychic damage if the spell fails.

Fell Rebuke. In response to being hit by an attack, Xowie utters a fell word, dealing 10 (3d6) necrotic damage to the attacker, and Xowie teleports, along with any equipment he is wearing or carrying, up to 30 feet to an unoccupied space he can see.

Xowie has 3 Legendary Actions.

Spellcasting (2 Actions): Xowie casts a spell or uses an action to use an effect of an ongoing spell, like Telekinesis.

Resurrect Goat (1 Action): Xowie resurrects a dead goat

Chill Touch (2 Actions): Xowie attacks with his chill touch. He cannot get an additional attack.