Ardreth, the World Ender

Fey Ancestry. Ardreth has advantage on saving throws he makes to avoid or end the charmed condition on itself, and magic can't put him to sleep.

Legendary Resistance (2/Day). If Ardreth fails a saving throw, he can choose to succeed instead.

Multiattack. Ardreth makes three Deathbringer attacks.

Deathbringer. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 15 (4d6 + 4) fire damage plus 15 (4d6+4) necrotic damage. Each attack creates a 20 ft. cone of demonic fire behind the attacked target. All creatures in the cone must make a DC 18 Dexterity saving throw, taking 11 (3d6 + 2) fire damage plus 11 (3d6 + 2) necrotic damage on a failed save, or half as much on a successful save. Ardreth heals for half the damage dealt.

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

Umbral Dash. Ardreth moves up to 20 ft., ignoring attacks of opportunity. At the end of his movement, he can make one Deathbringer attack against the nearest creature of his choice within range.

Infernal Chains (Costs 2 Actions). Ardreth conjures infernal chains around a target of his choice. The target must make a DC 18 Strength saving throw, taking 20 (3d12) fire damage and becoming restrained until the start of Ardreth's next turn on a failed save, and taking half as much damage and is not restrained on a successful save.

World Ender (Costs 3 Actions). Ardreth unleashes his demon form, sending out demonic energy within a 60 yd radius. Every creature of Ardreth's choice in this radius must make a DC 18 Constitution saving throw, taking 24 (4d12) necrotic damage on a failed save, or half as much damage on a successful save. While Ardreth is in this form, enemies that start their turn within 10 ft. of Ardreth must succeed on a DC 18 Wisdom saving throw or be frightened of Ardreth for 1 minute. A frightened target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a target's save is successful, the target is immune to this fear for 24 hours. This form lasts one hour and while in this form Ardreth can not use World Ender again.