Amon

Cunning Action. On each of Amon's turns he can use a bonus action to take the Dash, Disengage, or Hide action.

Innate Spellcasting. Amon's innate spellcasting ability is Charisma (Spell save is DC 21, +13 to hit with spell attacks). He can innately cast the following spells, requiring no material components:

At will: alter self ( can become Medium when changing his appearance), animate dead, charm person, detect magic, fireball, fly, geas, haste, invisibility (self only), polymorph

3/day: dispel magic, suggestion, wall of ice

1/day: Symbol (Pain only) 

Legendary Resistance (3/day). if Amon fails a saving throw, he can choose to succeed instead.

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

Magic Weapons. Amon's weapon attacks are magical.

Regeneration. Amon 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. Amon dies only if he starts his turn with 0 hit points and doesn't regenerate.

Multiattack. Amon makes three melee attacks: two with his thundering Heavy Mace, and one with his bite.

Bite. Melee Weapon Attack: +14 to hit, range 5 ft., one target. Hit: 14 (2d6 + 7) Piercing damage. If the target is a creature, it must succeed on a DC 22 Strength saving throw or be knocked prone.

Thundering Heavy Mace. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 20 (d8 + 7) piercing damage plus 13 (3d8) thunder damage. 

Wolf Howl (2/day). Amon howls, which causes 1d4+2 winter wolfs to appear in unoccupied spaces of his choice within 60 feet of him. the winter wolfs roll initiative when they appear. they remain until they die or Amon dismiss any or all of them.

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 (Costs 2 Actions). Amon attacks once with his thundering heavy mace.

Cry Havoc (Costs 3 Actions). Amon uses his wolf howl action if it is available. Amon then casts haste (it can be cast on him or one of the winter wolves).

Teleport. Amon uses his Teleport action.