Verazanoth

Spellcasting. The Verazanoth is a 19-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 24, +17 to hit with spell attacks).

Cantrips (at will): fire-bolt, ray of frost, toll the dead

1st level (6 slots): Ray of Sickness, Magic Missile, Shield, Chromatic Orb

2nd level (4 slots): Scorching Ray, Suggestion, Crown of Madness, Hold Person

3rd level (4 slots): Animate Dead, Bestow Curse, Fireball, Lightning Bolt, Counterspell

4th level (4 slots): Banishment, Blight, Wall of Fire, Phantasmal Killer, Festering Blast

5th level (4 slots): Cloudkill, Dominate Person, Cone of Cold, Scrying

6th level (2 slots): Disintegrate, Create Undead, Eyebite, Chain Lightning

7th level (2 slots): Finger of Death, Void Star, Power Word Pain

8th level (1 slot): Power Word Stun, Iron Body

9th level (1 slot): Wail of the Banshee, Power Word Kill, Detonate

Legendary Resistance. If Verazanoth fails a saving throw he can choose to succeed (3 per day)

Undead Fortitude. If damage reduces Verazanoth to 0 hit points, it must make a Constitution saving throw unless the damage is fire or from a critical hit. On a success, Verazanoth drops to 1 hit point instead.

Unholy Harboring. At the beginning of every turn Verazanoth begins to channel necrotic energy into a orb. This can be stopped with a 5th level dispel magic or dealing 50 damage in one moment to Verazanoth

Wail of The Dammed . If Unholy Harboring is uninterrupted before returning to Verazanoths turn he unleashes a blast of Necrotic energy that reaches 200ft in every direction. Each creature within the radius must make a Constitution saving throw taking 12d12 damage on and gaining one level of exhaustion on a failed save, on a success the creature suffers no effects.