Cherry Blome, Prince of the Morning Star

Telepathic Bond. Cherry ignores the range restriction on its telepathy when communicating with a creature he has charmed. The two don't even need to be on the same plane of existence.

Shapechanger. Cherry can use its action to polymorph into a Small or Medium humanoid, or back into its true form. Without wings, Cherry loses his flying speed. Other than his size and speed, his statistics are the same in each form. Any equipment he is wearing or carrying isn't transformed. He reverts to his true form if he dies.

Dueling. Cherry adds a +2 to rapier damage rolls (included in attack). 

Stabby Spell. If Cherry casts a spell, he can make one attack with Oblivion.

Spellcasting. Cherry's innate spellcasting ability is Charisma (spell save 19, +11 to hit on spell attacks). Cherry can innately cast the following spells, requiring no material components:
At will: charm person, crown of madness, detect magic, dispel magic, dissonant whispers
3/day each: counterspell, cure wounds, darkness, dominate person, telekinesis
1/day each: dominate monster, greater invisibility, synaptic static, Otto's Irresistible Dance

Legendary Resistance (3/Day). If Cherry fails a saving throw, he can choose to succeed instead.

Magic Resistance. Cherry has advantage on saving throws against spells and other magical effects.

Magic Weapons. Cherry weapon attacks are magical, dealing an extra 5d6 poison damage (included in attack).

Multiattack. Cherry makes two attacks with Oblivion. 

Oblivion. Melee Weapon Attack: +11 to hit, reach 5 ft, one target. Hit: 13 (1d8+7) piercing damage and 5d6 poison damage.  

Charm. One humanoid Cherry can see within 30 feet of it must succeed on a DC 17 Wisdom saving throw or be magically charmed for 1 day. The charmed target obeys his verbal or telepathic commands. If the target suffers any harm or receives a suicidal command, it can repeat the saving throw, ending the effect on a success. If the target successfully saves against the effect, or if the effect on it ends, the target is immune to his Charm for the next 24 hours.
Cherry can have only one target charmed at a time. If he charms another, the effect on the previous target ends.

Draining Kiss. Cherry kisses a creature charmed by himself or a willing creature. The target must make a DC 15 Constitution saving throw against this magic, taking 32 (5d10 + 5); psychic damage on a failed save, or half as much damage on a successful one. The target's hit point maximum is reduced by an amount equal to the damage taken. This reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0.

Etherealness. The fiend magically enters the Ethereal Plane from the Material Plane, or vice versa. 

Teleport. Cherry magically teleports up to 120 feet. 

Parry. Cherry adds 6 to his AC against one melee attack that would hit him. To do so, he must see the attacker and be wielding a melee weapon.

Attack. Cherry attacks once with Oblivion
Dance, My Puppet. One creature charmed by Cherry that Cherry can see must use its reaction to move up to its speed as Cherry directs.
Sow Discord. Cherry casts crown of madness or dissonant whispers.
Teleport. Cherry uses his Teleport action.