Ak'chazar Rakshasa

Limited Magic Immunity. The ak'chazar 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 ak'chazar rakshasa's innate spellcasting ability is Charisma (spell save DC 20, +12 to hit with spell attacks). The ak'chazar rakshasa can innately cast the following spells, requiring no material components:

At will: detect thoughts, disguise self, mage hand, minor illusion

3/day each: charm person, detect magic, invisibility, major image, power word pain, suggestion

1/day each: dominate person, fly, magic jar, plane shift, true seeing

Spellcasting. The ak'chazar rakshasa is a 14th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 17, +9 to hit with spell attacks). The ak'chazar rakshasa has the following wizard spells prepared:

Cantrips (at will): chill touch, dancing lights, mage hand, ray of frost

1st level (4 slots): false life, ray of sickness, shield

2nd level (3 slots): acid arrow, blindness/deafness, hold person, ray of enfeeblement

3rd level (3 slots): animate dead, counterspell, dispel magic, summon undead

4th level (3 slots): blight, dimension door, polymorph

5th level (2 slots): cloudkill, danse macabre, negative energy flood

6th level (1 slot): circle of death, create undead, soul cage

7th level (1 slot): finger of death

Multiattack. The ak'chazar rakshasa makes three claw attacks.

Claw. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 10 (2d6 + 3) slashing damage, and the target is cursed if it is a creature. The magical curse takes effect whenever the target takes a short or long rest, filling the target's thoughts with horrible images and dreams. The cursed target gains no benefit from finishing a short or long rest. The curse lasts until it is lifted by a remove curse spell or similar magic.

Command Undead (3/day). As an action, the ak'chazar rakshasa attempts to assert control over up to ten uncontrolled undead with a collective challenge rating equal to or less than 10 that it can see within range. If the ak'chazar rakshasa targets more than one undead, it must be within 30 feet of the other undead target(s). The undead must succeed on a DC 20 Wisdom saving throw or be subject to the ak'chazar rakshasa's control for the next 24 hours as per the animate dead spell. If the ak'chazar rakshasa or creatures friendly to it are fighting a target, it has advantage on the saving throw. Undead already under the control of another creature automatically succeed on the saving throw. In order to maintain control over an undead of challenge rating 1 or higher, the ak'chazar rakshasa must use this power again rather than animate dead to reassert its control over it. 

Bolster Undead (9/day). As an action, the ak'chazar rakshasa emits an aura of negative energy. Any undead creature within 60 feet of the ak'chazar rakshasa gains advantage on saving throws against turning, disadvantage on saving throws against command undead cast by the ak'chazar rakshasa, and resistance to radiant damage for the next minute.