Belial

Fear aura. Any creature hostile to Belial that starts its turn within 20ft of Belial must make a DC 26 Wisdom saving throw, unless Belial is incapacitated. On a failed save, the creature is frightened until the start of its next turn. If a creature's saving throw is successful, the creature is immune to Belial's Fear Aura for the next 24 hours.

Devil’s Sight. Magical darkness doesn’t impede Belial's darkvision.

Magic Weapons. Belial's weapon attacks are magical.  has the following item on his person: +3 Wracking Glaive known as Pain's cinders. 

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

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

Regeneration. Belial regains 20 hit points at the start of his turn. If he takes radiant damage, this trait doesn’t function at the start of his next turn. Belial dies only if he starts his turn with 0 hit points and doesn’t regenerate.

Innate Spellcasting. Belial’s innate spellcasting ability is Charisma (spell save DC 26 +18 to hit). Belial can innately cast the following spells, requiring no material components:

At will: Charm monster, Darkness (5th level), Detect good and evil (Good only), Detect magic, Dispel magic (6th level), Hellflame blast*, Locate creature, Locate object, Produce flame, See invisibility, Suggestion, Wall of fire

3/day each: Geas, Greater restoration, Major image, Raise dead

1/day each: Dominate monster, Symbol (Pain only), Wish
* Means the spell is within Hellish depths pdf.

Multi attack. Belial makes four attacks with Pain's cinders. 

Pain's cinders. Melee Weapon Attack: +20 to hit, reach 10 ft., 1 target. Hit: 23 (2d10 + 12) slashing damage and the target must make a DC 18 Constitution saving throw or be stunned until the end of their next turn. 

Teleport. Belial magically teleports, along with any equipment he is wearing and carrying, up to 120 feet to an unoccupied space he can see.

Summon Devil (3/Day). Belial chooses what to summon and attempts a magical summoning.

Belial has a 100 percent chance of summoning 1d10 Bearded devils or 1d8 Barbed devils.

Belial has a 100 percent chance of summoning 1 pit fiend. 

A summoned devil appears in an unoccupied space within 60 feet of Belial, acts as an ally of Belial, and can’t summon other devils. It remains for 1 minute, until it or Belial dies, or until Belial dismisses it as an action.

Belial 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. Belial regains spent legendary actions at the start of his turn.

Cast a Spell (Costs 1 Action). Belial casts a spell from their Innate spellcasting. 

Teleport (Costs 1 Action). Belial uses his Teleport action. 

Commandment of the Judge (Costs 2 Actions). Belial shouts a command to 3 or less devils within 60ft of Belial that can hear him must use their reaction to either move half their movement speed in a direction of his choice or make one attack against a target of his choice. 

Hellish Pain (Costs 3 Actions). Belial touches one creature adjacent to himself causing them to make a DC 25 Constitution saving throw or take 35 (10d6) psychic damage and be stunned until the end of their next turn.