Ak'chazar

Limited Magic Immunity. The rakshasa can't be affected or detected by spells of 6th level or lower unless it wishes to be. It has advantage on saving throws against all other spells and magical effects.

Innate Spellcasting. The rakshasa's innate spellcasting ability is Charisma (spell save DC 18, +10 to hit with spell attacks). The rakshasa can innately cast the following spells, requiring no material components:

At will: detect thoughts, Disguise self, Invisibility

3/day each: Animate Dead, detect magic

2/day each: Create Undead, Danse Macabre

1/day each: Magic Jar

Spellcasting. The Ak'chazar is an 12th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 18, +10 to hit with spell attacks). The Ak'chazar has the following sorcerer spells prepared:

Cantrips (at will): fire bolt, light, mage hand, prestidigitation, shocking grasp, Minor Illusion

1st level (4 slots):  magic missile, Ray of Sickness

2nd level (3 slots): mirror image, Crown of Madness

3rd level (3 slots): counterspell, enemies abound, lightning bolt

4th level (2 slots): Confusion, Dimension Door

5th level (2 slots): Enervation, Hold Monster

6th level (1 slot): Disintegrate

Channel Divinity - Rebuke Undead  (2/day):  As an action, the Ak'chazar can rebuke the undead.  Each undead that can see or hear the Ak'chazar within 30 feet of it must make a wisdom saving throw.  If the create fails its saving throw; it is turned for 1 minute or until it takes any damage. 

A turned creature must spend its turns trying to move as far away from you as it can, and it can’t willingly move to a space within 30 feet of you. It also can’t take reactions. For its action, it can use only the Dash action or try to escape from an effect that prevents it from moving. If there’s nowhere to move, the creature can use the Dodge action.

If the undead is has a CR of 4 or lower, the undead is instead under the effect of a Dominate Monster but it specifically affects only undead and requires no concentration.

Multiattack. The Ak'chazar makes two claw attacks and a bite attack.

Claw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 9 (1d4 + 2) slashing damage.

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 9 (1d6 + 2) slashing damage.

Pain Wave. Three times per day an Ak'Chazar can emit an aura of negative energy.  Every creature within 20 feet when it activates the ability is wounded for 2d6+24 damage (32 average).  Creatures may make a DC 18 Wisdom saving throw for half damage