Belphegor, Agent of Chaos

Innate Spellcasting. Belphegor is a 17th-level spellcaster. His spellcasting ability is Charisma (spell save DC 25, +18 to hit with spell attacks). Belphegor can cast the following spells, requiring no material components:

At Will: Sword Burst, Vicious Mockery, Detect Magic, Tasha’s Hideous Laughter, Cloud of Daggers, Misty Step, Hold Monster, Glibness

3/Day Each: Crown of Madness, Counterspell, Dispel Magic, Enemies Abound, Mislead, Seeming, Synaptic Static, Mental Prison, Programmed Illusion, Teleport

1/Day Each: Maddening Darkness, Imprisonment (1 Action), Psychic Scream, Weird

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

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

Magic Weapons. Belphegor’s weapon attacks are magical.

Mindbreaker. Belphegor’s attacks ignore resistance to Psychic damage. Additionally, any creature who targets Belphegor with Psychic damage becomes vulnerable to it until the end of Belphegor’s next turn.

Last Laugh (1/Day). When Belphegor reaches 0 hit points, he attempts a DC 20 Constitution Saving Throw. On a successful save, he releases all the souls around him in a radius of 500 feet, causing 25d6 Cold damage, and all creatures who fail a DC 25 Con save are blinded for a minute, but can repeat saving throws at the end of their turn. This effect is stressful enough to end all effects requiring Concentration. Belphegor then stands up with 1 hit point and immediately attempts to teleport. Belphegor then loses his Devour Soul Legendary Action for the rest of the day. If Belphegor's teleport attempt fails, his souls begin attempting to grapple him.

Sentient Chains. While wearing the Coat of Chaos, Belphegor’s chains automatically release themselves to protect their true master if he is unable to catch himself, making him immune to falling Prone. Additionally, they attempt to pull off any attacker who has Belphegor Grappled, or Restrained. This grants Belphegor advantage on escape attempts, and grants the opposing creature disadvantage to hold Belphegor.

Multiattack. Belphegor can activate his Aura of Insanity. He may then make 3 Abyssal Chain attacks, or throw 2 Daggers of Madness.

Abyssal Chain. Melee Weapon Attack: +18 to hit, reach 15 ft., 1 target. Hit. (3d10 + 10) Slashing damage and (1d10) Psychic damage.

Dagger of Madness. RangedWeapon Attack: +18 to hit, range 200 ft., 1 target. Hit: (5d4 + 10) Piercing damage and (1d10) Psychic damage. This attack ignores any benefit gained from non-full cover.

Aura of Insanity. Belphegor begins to act frenzied and erratic. All creatures within 50 feet of Belphegor and are aware of his presence must make a DC 25 Wisdom Saving Throw or become Frightened of Belphegor. A creature who passes is immune to this effect for 1 hour. A creature who is Frightened of Belphegor takes (5d12) Psychic damage at the start of their turn. At the end of the creature’s turn, they can attempt to remake the Saving Throw. A creature who is reduced to 0 hit points by this ability is under the effect of the Feeblemind spell when stabilized, Resurrected, etc. However, only Wish can end the effect.

Wild Wheezing (Recharge 5-6). Belphegor begins to cough and wheeze out corrupted magic in a 100 foot cone, which spreads around corners. Any creature, other than Belphegor who casts a spell in the affected area rolls a d20. On a roll of 1-5, the spell fails, and an effect from the Wild Magic Surge table occurs. If the spell is a Divination spell, it fails on a roll of 1-10.

Cloud of Daggers. Belphegor casts Cloud of Daggers as a Bonus Action.

Tripping Over Yourself. A creature who enters within 15 feet of Belphegor that he can see must pass a DC 20 Dexterity Saving Throw, as Belphegor attempts to swipe at their legs, or pull them from out of the air. On a failed save, the creature takes (1d10) Bludgeoning damage, and lands prone. The creature’s turn then ends.

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

Now I… Disappear! (Costs 1 Action). Belphegor casts Misty Step.

Dagger of Madness (Costs 1 Action). Belphegor makes an attack with a Dagger of Madness.

Devour Soul (Costs 2 Actions). Belphegor devours one of the souls surrounding him, and heals 2d10 + 5 hit points, and gains 10 temporary hit points.