Agares

Aura of Fear. At the end of each of Agares’s turns, creatures within 100 feet of him must make DC 18 Charisma saving throw or be frightened for one minute. A creature that successfully saves cannot be affected again by Agares’s aura for 24 hours. Other devils are immune to the aura.

Brand of Levistus. Agares' natural attacks deal an extra 1d6 points of cold damage (included).

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

Magic Weapons. Agares' weapon attacks are magical.

Regeneration. Agares regains 10 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. Agares does not regenerate if he starts his turn with 0 hit points.

Innate Spellcasting. Agares can cast the following spells, requiring no material components:
At will: dispel magic, earthquake, ice storm, see invisibility, slow, teleport, wall of ice 
1/day: summon fiend (65% chance to summon 1d6+2 bone devils), symbol (pain)

Spellcasting. Agares is a 20th-level spellcaster. His spellcasting ability is Wisdom (spell save DC 22, +14 to hit with spell attacks). Agares has following Cleric spells prepared:
Cantrips (at will): resistance
1st level (5 slots): bane, command, divine favor, inflict wounds, sanctuary, shield of faith
2nd level (4 slots): blindness/deafness, calm emotions, hold person, silence, zone of truth
3rd level (4 slots): bestow curse, magic circle, sending, water walk
4th level (3 slots): banishment, locate creature
5th level (3 slots): dispel evil and good, flame strike, geas, mass cure wounds, planar binding
6th level (3 slots): blade barrier, harm, hold monster
7th level (2 slots): hellfire storm
8th level (2 slots): antimagic field, unholy aura
9th level (2 slots): implosion, soul bind

Implosion. Agares creates a destructive resonance in a corporeal creature’s body. For each round he concentrates (up to 4), he causes one creature to collapse in on itself, killing it unless they succeed on a DC22 Constitution saving throw.  Implosion has no effect on creatures in gaseous form or incorporeal creatures.

Soul Bind. Agares draws the soul from a newly dead body and imprisons it in a black sapphire gem. The subject must have been dead no more than 30 minutes. The soul, once trapped in the gem, cannot be returned through raise dead, reincarnation, resurrection, true resurrection, or wish. Only by destroying the gem or dispelling the spell on the gem can one free the soul (which is then still dead).

Multiattack. Agares makes two attacks with his staff or two attacks with his claws.

Iron-Shod Staff. Melee Weapon Attack: +20 to hit, reach 10 ft., one target. Hit: 19 (1d8 + 13) bludgeoning damage. 

Claws. Melee Weapon Attack: +15 to hit, range 10 ft., one target. Hit: 13 (1d6 + 8) slashing damage plus 4 (1d6) cold damage.

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

Tomb of Levistus. When Agares takes damage, he can entomb himself in ice, which melts away at the end of his next turn. He gains 280 temporary hit points, which take as much of the triggering damage as possible. Immediately after he takes the damage, he gains vulnerability to fire damage, his speed is reduced to 0, and he is incapacitated. These effects, including any remaining temporary hit points, all end when the ice melts.  Agares can use this invocation once per short or long rest.

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

Attack. Agares makes one attack with his staff or claws.

Cast a Spell (Costs 2 Actions). Amon casts a spell from his list of spells of 5th level or lower.

Teleport. Amon uses his Teleport action.