Vyrmolder, Baron of Night

Cursed to never fly again.
Vyrmolter has only one wing and cannot fly properly. Meaning he cannot perform any airborne maneuvers that require full wingspan (e.g., Dive, Soar). 

Servant of the Nightlord.
While any allies are within 120 feet of Vyrmolter, they have advantage on all saving throws and deal an additional (2d6) cold damage with all attacks.

Legendary Resistance (3/Day).
If Vyrmolter fails a saving throw, he can choose to succeed instead.

Abominable Presence.
Each creature of Vyrmolter’s choice that is within 120 feet and aware of him must succeed on a DC 19 Wisdom saving throw or be frightened for 1 round. A frightened target can repeat the save at the end of each of its turns.

Nightfire Breath (Recharge 5–6).
Vyrmolter unleashes a 90-foot cone of blue-black flame. All creatures in the area must make a DC 21 Dexterity saving throw, taking 66 (6d20) cold and fire damage on a failed save, or half as much on a success. Creatures reduced to 0 HP by this ability rise the next round as Night Thralls.

Multiattack. Vyrmolter makes three attacks:
one with his bite and two with his claws.

Bite. Melee Weapon Attack: +17 to hit, reach 15 ft., one target.
Hit: 28 (4d10 + 6) piercing damage + 18 (4d8) cold damage.

Claw. Melee Weapon Attack: +17 to hit, reach 10 ft., one target.
Hit: 20 (3d8 + 6) slashing damage.

Tail. Melee Weapon Attack: +17 to hit, reach 20 ft., one target.
Hit: 24 (3d10 + 6) bludgeoning damage. If the target is Large or smaller, it must succeed on a DC 20 Strength saving throw or be knocked prone.

Vyrmolter can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time, and only at the end of another creature’s turn. He regains spent legendary actions at the start of his turn.

Body Slam (Costs 2 Actions).
Despite his crippled wings, Vyrmolter slams his body into the ground. All creatures within 15 feet must succeed on a DC 19 Dexterity saving throw or take 22 (4d10) bludgeoning damage and be knocked prone.

Bend the Night. (1/Day)
He defies the Nightlord, bending the power of the night to regrow his missing wings temporarily. Granting him 140ft of flight for the round, once it ends, he slams into the ground, triggering the Body Slam legendary action,

Summon Night Thralls (Costs 3 Actions).
Vyrmolter vomits a necrotic cocoon that bursts next round into 1d6 Night Thrall(s).