Large humanoid demon (shapechanger), chaotic neutral

Armor Class: 22 (Natural Armor)

Hit Points: 945 (90d8) + 540

Speed: 60 ft , fly: 120 ft

STR

15 +2

DEX

24 +7

CON

22 +6

INT

23 +6

WIS

23 +6

CHA

29 +9

Skills:
Avoidance. If Kairon has to make saving throw to take only half damage, he instead takes no damage if he succeeds and half damage if he fails.
Ki. Kairon has a pool of Ki points which he can use to fuel his abilities. Kairon has a maximum of 20 ki points.
Legendary Resistance (3/Day). If Kairon fails a saving throw, he can choose to succeed instead.
Shapechanger. Kairon can use his action to polymorph into a form that resembles a Medium humanoid, or back into his true form. Aside from his size, his statistics are the same in each form. Any equipment he is wearing or carrying isn't transformed.
Magic Resistance. Kairon has advantage on saving throws against spells and other magical effects.
Magic Weapons. Kairon's weapon attacks are magical.
Mastery of Death. When Kairon would reduce a creature to 0 hit points, he regains 30 hit points, a ki point, and may make an additional unarmed strike attack or short sword attack. When Kairon would be reduced to 0 hit points, he may expend a ki point (no action required) to instead be reduced to 1 hit point.
Necrotic Absorbtion. When Kairon would take necrotic damage he instead heals for half the damage that would be dealt to him.
Reactive. Kairon gains an additional reaction on each of his turns.
Unerring Charm. Whenever a creature targets Kairon with an attack or a harmful spell they must make a Charisma saving throw (DC 24. On a failure, the creature must choose a new target or lose the attack or spell. On a success or when attacked by Kairon, the creature is no longer affected by Unerring Charm for the next 24 hours. Additionally, Kairon has advantage on any Charisma rolls he makes.

Damage Resistances: Acid, Lightning, Bludgeoning, Slashing, and Piercing

Damage Immunities: Cold, Fire, Psychic, Poison; Bludgeoning, Slashing, and Piercing from Nonmagical Attacks.

Condition Immunities: Charmed, Frightened, Exhausted, and Paralyzed

Senses: Truesight 120ft

Challenge Rating: 24

Actions

Multiattack. Kairon makes two attacks with his Short Sword, Fire Ray, or Cruel Grasp and then makes two Unarmed Attacks or a Draining Kiss Attack. Alternatively Kairon may make four attacks with his Short Sword.
  Shortsword. Melee Weapon Attack: +19 to hit, 10ft reach, one target. Hit: 15 (1d12+12) slashing damage + 6 (1d12) fire damage + 6 (1d12) necrotic damage + 6 (1d12) chaos damage. Additionally, if the target is humanoid, it must make a DC 20 Constitution saving throw. On a failure, the creature becomes cursed, the curse can be removed by Remove Curse or another similar spell of 3rd level or higher. While cursed in this way, the creature cannot regain hit points, after a minute the curse ends, and the creature becomes afflicted with Abyssal Corruption. While afflicted with Abyssal Corruption, the creatures skin darkens, and their sclera turn black, the creature can speak and understand abyssal but loses it abilities to speak and understand any other language. Additionally, when the creature is outside of the abyss it cannot regain hit points and takes 10 (3d6) fire damage every 10 minutes. The affliction can be removed by Heal or another similar spell of 6th level or higher.
  Unarmed Attack. Melee Unarmed Attack: +16 to hit, 10ft reach, one target. Hit 28 (3d12+9) bludgeoning damage.
  Fire Ray. Ranged Spell Attack: +16 to hit, 120ft reach, one target. Hit: 27 (5d10) fire damage.
  Cruel Grasp. Ranged Spell Attack: +16 to hit, 60ft reach, one target. Hit 18 (4d8) necrotic damage. The target must make a DC 24 Strength saving throw. On a failure, the creature is restrained until the end of their next turn and is moved up to 15ft in a direction of Kairon's choice.
  Draining Kiss. Kairon kisses a creature restrained by him or a willing creature. The creature must make a DC 24 Constitution saving throw. On a failure, the creature takes 37 (5d10+10) psychic damage, or half as much on a successful save. The creature takes double damage if it is charmed by Kairon. The target's hit point maximum is reduced by an amount equal to the damage taken and Kairon regains a number of hit points lost this way. This reduction lasts until the target takes a long rest. The target transforms into a Incubus/Succubus if this effect reduces the target's hit point maximum to 0.   Coerce (Recharge 5-6). Kairon targets one creature he can see within 60ft. The target must decide whether or not to become charmed by Kairon. If the creature chooses not to be charmed, they must make a DC 24 Constitution saving throw. On a failure, the creature takes 55 (10d10) psychic damage, or half as much on a successful save. If the creature chooses to be charmed, they fall under the control of Kairon bypassing any immunities to being charmed that the creature may have. The creature may make a DC 24 Wisdom saving throw at the end of each of its turns. On a success, the creature is no longer charmed
  Enslave (3/Day). Kairon targets one creature he can see within 30 feet. The target must succeed on a DC 24 Wisdom saving throw or be magically charmed by Kairon until he dies or until he is on a different plane of existence from the target. The charmed target is under Kairon’s control and can’t take reactions, and he and the target can communicate telepathically with each other over any distance.
Whenever the charmed target takes damage, the target can repeat the saving throw. On a success, the effect ends. No more than once every 24 hours, the target can also repeat the saving throw when it is at least 1 mile away from Kairon. The effect becomes permanent after a year has passed, changing the creature's alignment to fit Kairon's.

Legendary Actions

Kairon 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. Kairon regains spent legendary actions at the start of its turn.
  Attend Me. Kairon targets a creature under his control immediately moving it up to its movement speed and it takes an action.
  Short Sword. Kairon makes one attack with his short sword against a creature within range.
  Teleport. Kairon teleports to an empty location within 60ft of him.
  Demonic Supremacy (Costs 2 Actions). Kairon casts a spell which he could cast innately.