Champion of Norganas

Dark Power. Never needs air, food, drink or sleep. Cannot be disarmed or banished.

Legendary Resistance (1/Day). If the Champion fails a saving throw, it can choose to succeed instead.

Spellcasting. The Champion is a 5th-level spellcaster. Its spellcasting ability is 5 (spell save DC 18, +10 to hit with spell attacks). The Champion has the following Warlock spells prepared:
Cantrips (at will): Eldritch Blast, Fog Cloud, Green-Flame Blade
5th level (Once each): Burning Hands, Command, Fire Shield, Fireball, Scorching Ray, Stinking Cloud, Thunder Step, Wall of Fire

Multiattack. The champion makes two Scythe attacks, one of which can be replaced by a Finger of Death. if available.

Scythe. Melee Weapon Attack: +9 to hit, reach 10 ft. Hit: (2d8 + 5) [Necrotic] damage. Regain health equal to damage dealt.

Finger of Death (Recharge 5+). Ranged Spell Attack: Instantaneous, range 30 ft, verbal and somatic. Target makes a Con 18 saving throw. Hit:  (7d8 + 30) [Necrotic] damage.

Plane walk. As a bonus action, the champion may move to or from the Ethereal plane. While in the Ethereal plane, the champion may not interact with the Material plane or be acted upon by the Material.

Phase out. As a result of taking damage, the champion may retreat to the ethereal plane.

Hellish Rebuke. The creature that damaged you is momentarily surrounded by green flames. It makes a Dexterity saving throw, taking 6d10 Fire damage on a failed save or half as much damage on a successful one.

Counterspell. You attempt to interrupt a creature in the process of casting a spell. The creature makes a Constitution saving throw. On a failed save, the spell dissipates with no effect, and the action, Bonus Action, or Reaction used to cast it is wasted. If that spell was cast with a spell slot, the slot isn’t expended.