Avatar of Chemosh

Pestilent Undead  (Recharges after a Short or Long Rest). If the Avatar would be reduced to 0 hit points, his current hit point total instead resets to 500 hit points, he recharges his Necrotic Flames, and he regains any expended uses of Legendary Resistance. Additionally, the aspect can now use the options in the "Mythic Actions" section for 1 hour. 

Legendary Resistance (5/Day). If the avatar fails a saving throw, he can choose to succeed instead.

Multiattack. The avatar makes one Claw attack, one Scythe attack, and one Tail attack.

Claw. Melee Weapon Attack: +19 to hit, reach 20 ft., one target. Hit: 23 (2d12 + 10) piercing damage plus 19 (3d12) force damage.

Scythe. Melee Weapon Attack: +19 to hit, reach 15 ft., one target. Hit: 21 (2d10 + 10) slashing damage. If the target is a Huge or smaller creature, it is grappled (escape DC 20) and is restrained until this grapple ends. The avatar can have only one creature grappled this way at a time.

Tail. Melee Weapon Attack: +19 to hit, reach 15 ft., one target. Hit: 23 (2d12 + 10) bludgeoning damage. If the target is a creature, it must succeed on a DC 27 Strength saving throw or be knocked prone.

Necrotic Flames (Recharge 5–6). The avatar exhales multicolored flames in a 300-foot cone. Each creature in that area must make a DC 27 Dexterity saving throw. On a failed save, the creature takes 71 (11d12) damage of a type of the avatar’s choosing: acid, cold, fire, lightning, or poison. On a successful save, the creature takes half as much damage.

The avatar 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. The aspect regains spent legendary actions at the start of her turn.

Attack. The avatar makes one Claw or Tail attack.

UnGodly Scythe (Costs 2 Actions). The avatar makes one Scythe attack. If the attack hits a creature, the target must succeed on a DC 27 Wisdom saving throw or become incapacitated until the end of its next turn.

If the avatar’s Pestilent Undead trait has activated in the last hour, he can use the options below as legendary actions.

Hurl Through the Hall of Souls Costs 2 Actions). The avatar targets a creature he is grappling. The creature must succeed on a DC 25 Charisma saving throw or take 44 (8d10) psychic damage and be banished to the Hall of Souls. At the start of the avatar’s next turn, the creature reappears in an unoccupied space within 10 feet of the avatar

Necrotic Nova (Costs 3 Actions). The avatar erupts with soul energy from the Hall of Souls. Each creature of the avatar’s choice in a 60-foot-radius sphere centered on him must make a DC 27 Dexterity saving throw. On a failed save, the creature takes 39 (6d12) damage of a type chosen by the avatar: acid, cold, fire, lightning, or poison. On a successful save, the creature takes half as much damage.