Amon the Wolf

Fear Aura. Amon permeates an aura of fear in a 20-foot radius.  The aura acts similarly to a fear spell.  Any non-devil within the radius must make a DC 18 Wisdom save.  On a success, that creature cannot be affected again by Amon's fear aura for one day.

Great Cleave. If Amon defeats a creature (typically by dropping it to below 0 hit points or killing it), he gets an immediate, extra melee attack against another creature within reach. He cannot take a 5-foot step before making this extra attack. The extra attack is with the same weapon and at the same bonus as the attack that dropped the previous creature.  

Improved Initiative. Amon gains a +5 bonus to initiative checks.

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

Magic Weapons. Amon's weapon attacks are magical.

Innate Spellcasting. Amon is an 18th-level spellcaster. His spellcasting ability is Charisma (spell save DC 18, +10 to hit with spell attacks). Amon can cast the following spells, requiring no material components:
At will: animate dead, charm person, cone of cold, create undead, detect magic, dispel magic, fly, greater invisibility, major image, polymorph, suggestion, teleport, unholy aura, unhallow, wall of ice
2/day: summon fiend (either two bone devils or bearded devils; or one erinyes, horned devil, or ice devil
1/day: limited wish, symbol (hopelessness)

Power Attack. Before making an attack roll for the round, Amon may choose to subtract a number from all melee attack rolls and add the same number to all melee damage rolls. This number may not exceed his base attack bonus. The penalty on attacks and bonus on damage apply until his next turn.

If Amon attacks with a two-handed weapon, or with a one-handed weapon wielded in two hands, instead add twice the number subtracted from his attack rolls.

Regeneration. Amon 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. Amon does not regenerate if he starts his turn with 0 hit points.

Multiattack. Amon makes two attacks with his mace and one attack with his bite.

Gargantuan Heavy Mace. Melee Weapon Attack: +19 to hit, reach 10 ft., one target. Hit: 27 (4d6 + 13) bludgeoning damage plus 10 (3d6) cold damage. 

Bite. Melee Weapon Attack: +16 to hit, range 5 ft., one target. Hit: 19 (2d8 + 10) piercing damage.

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

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

Attack. Amon makes one attack with his mace or bite.

Cast a Spell (Costs 2 Actions). Amon casts a spell from his list of spells.

Teleport. Amon uses his Teleport action.