Ice Walk. The dragon can move across and climb icy surfaces without needing to make an ability check. Additionally, difficult terrain composed of ice or snow doesn't cost it extra movement.

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

Gust of Wind (1/Day). The dragon can cast Gust Of Wind once per day.

Multiattack. The dragon makes three attacks: one with its bite and two with its claws.

Bite. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 15 (2d10 + 4) piercing damage plus 4 (1d8) cold damage.

Claw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 11 (2d6 + 4) slashing damage.

Tail. Melee Weapon Attack: +7 to hit, reach 15 ft., one target. Hit: 13 (2d8 + 4) slashing damage.

Cold Breath (Recharge 5–6). The dragon exhales an icy blast in a 30-foot cone. Each creature in that area must make a DC 15 Constitution saving throw, taking 45 (10d8) cold damage on a failed save, or half as much damage on a successful one.

Vengeful Mother. Each time a white dragon wyrmling is killed within sight off this creature, it immediately make a bite attack on creature that killed the wyrmling. If out of range, then the closest creature to the dragon.

Lair Action: The North Wind. On initiative count 20 (losing initiative ties) the dragon takes a layer action to cause the following effect. Each creature besides the dragon in area H20 of Icespire Hold must succeed a DC 15 Constitution saving throw or take 2d6 cold damage and be pushed 10 feed south.