Cryovain the Dragon Wraithlord

Driven from lands farther north by more powerful dragons, the white dragon, Cryovain, descended upon the Sword Mountains, claiming the snow-capped range as its domain. Typical of its kind, Cryovain was dim-witted and cruel. The dragon patrolled the skies around Icespire Peak, surveying its territory while hunting for food and easy treasure. With each passing day, the dragon’s domain grew as it ranged farther across the land, preying on anything it could catch with its claws or freeze to death with its icy breath. Sightings of the dragon were becoming more common, as were its attacks.

A crumbling fortress on the northeast spur of Icespire Peak served as the dragon’s lair. Cryovain seized the icy fortress from a tribe of savage orcs, killing the orc war chief and forcing the tribe’s survivors to flee into the foothills and forests. 

Cryovain's constant forays drew the attention of a the people of Phandalin, and they encouraged a local group of heroes to seek ways to protect the town from the dragon.  Over time, the heroes gained enough strength to challenge Cryovain and sought out the dragon in its lair.  Following a challenging fight, the heroes of Phandalin managed to slay Cryovain.

Unfortunately, they were unaware that a local necromancer had taken an interest in the dragon.  Upon Cryovain's death, the necromancer made his way to Icespire Hold and, using his necrotic magics, summoned back Cryovain's spirit.  The magic transformed Cryovain into a Dragon Wraithlord, a creature of pure evil and incredible power.

Cryovain remembers his death and has vowed to seek vengeance on those that originally slew him.

Lair Actions

On initiative count 20 (losing initiative ties), Cryovain takes a lair action to cause one of the following effects; Cryovain can’t use the same effect two rounds in a row:

• Freezing fog fills a 20-foot-radius sphere centred on a point Cryovain can see within 120 feet of it. The fog spreads around corners, and its area is heavily obscured. Each creature in the fog when it appears must make a DC 10 Constitution saving throw, taking 10 (3d6) cold damage on a failed save, or half as much damage on a successful one. A creature that ends its turn in the fog takes 10 (3d6) cold damage. A wind of at least 20 miles per hour disperses the fog. The fog otherwise lasts until Cryovain uses this lair action again or until Cryovain dies.
• Jagged ice shards fall from the ceiling, striking up to three creatures underneath that Cryovain can see within 120 feet of it. Cryovain makes one ranged attack roll (+7 to hit) against each target. On a hit, the target takes 10 (3d6) piercing damage.
• Cryovain creates an opaque wall of ice on a solid surface it can see within 120 feet of it. The wall can be up to 30 feet long, 30 feet high, and 1 foot thick. When the wall appears, each creature within its area is pushed 5 feet out of the wall’s space, appearing on whichever side of the wall it wants. Each 10-foot section of the wall has AC 5, 30 hit points, vulnerability to fire damage, and immunity to acid, cold, necrotic, poison, and psychic damage. The wall disappears when Cryovain  uses this lair action again or when Cryovain dies.