Aelzeroth of the Mirror

Magical Karma. If a creature scores a critical hit on Aelzeroth, then Aelzeroth's next attack against that creature is an automatic critical hit.

Mirror Image. Once a day Aelzeroth can summon mirror images of all his enemies in the battle. The mirror images have 1/4 the hit points of the originals, and an armor class of 16. They have all the same abilities as the originals, but only deal half damage. The mirror images have an initiative one point higher than the originals.

Magic Mirror. Aelzeroth has a magic mirror that reflects all incoming spells back at the user, requiring them to make the save, or roll to hit. The save or hit is based on the one who sent it. Aelzeroth can summon this mirror twice a day as a bonus action. Each mirror has an armor class of 17, and 45 hit points.

Strong Will. Aelzeroth can have up to two concentrations spells going at once. He also has advantage on concentration checks.

Spellcasting. Aelzeroth is an 20th-level spellcaster. His spellcasting ability is Intelligence (spell save DC 19, +11 to hit with spell attacks).

Aelzeroth can cast levitate and invisibility at will and can cast spells from multiple classes listed below.

Cantrips (at will): fire bolt, vicious mockery, eldritch blast, toll the dead, shocking grasp

1st level (4 slots): earth tremor, chaos bolt, entangle, magic missile

2nd level (3 slots): dust devil, mirror image, misty step

3rd level (3 slots): counterspell, [Tooltip Not Found], lightning bolt

4th level (3 slots): dimension door, fire shield, storm sphere

5th level (3 slots): cone of cold, destructive wave, antilife shell

6th level (1 slot): wall of ice

7th level (1 slot): mirage arcane, 

8th level (1 slot): illusory dragon

9th level (1 slot): invulnerability

*Aelzeroth casts the illusory dragon, and the mirror image spell before combat, along with the antilife shell spell on himself before combat.