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, mage hand, minor illusion

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

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

Learned Spellcasting. The rakshasa's spellcasting ability is Charisma (spell save DC 18, +10 to hit with spell attacks). 

Aadamakhor is a 9th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 18, +10 to hit with spell attacks). She has following bard spells prepared:
Cantrips (at will): Mage Hand, Message, Vicious Mockery
1st level (4 slots): charm person, command, silvery barbs, thunderwave
2nd level (3 slots): Blindness/Deafness, detect thoughts, mirror image
3rd level (3 slots):  hypnotic pattern, slow, counterspell
4th level (3 slots): dimension door, greater invisibility

5th level (1 slots): animate objects, dream, geas, scrying

Multiattack. The rakshasa makes two claw attacks.

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

Hellish Rebuke (Recharge 5-6)  When Aadamakor takes damage they may cast the hellish rebuke Spell for free without spending material components or spell slots.

Aadamakhor can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. Aadamakhor regains spent legendary actions at the start of its turn.

Claw: Aadamakhor makes a claw attack

Cantrip: Aadamakhor casts a Cantrip

Illusory Escape (Costs 2 Actions): The Rakshasa becomes invisible and moves up to its speed. They cease to be invisible at the end of their movement.