Cryovain

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.

Bite. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 15 (2d10 + 4) piercing damage plus 9 (2d8) cold damage.

Icy Layer. Cryovain slams his claws on the ground, covering it in ice. All ground within 40 feet of him is is covered with slick ice, making it difficult terrain. When a creature enters the area for the first time on a turn or starts its turn there, it must make a DC 12 Dexterity saving throw. On a failed save, it falls prone. If a creature is concentrating in the spell’s area, the creature must make a successful DC 12 Constitution saving throw or lose concentration. These effects last until the end of Cryovain's next turn.

Cold Breath. Cryovain exhales an icy blast in a 30-foot cone. Each creature in that area must make a DC 15 Constitution saving throw, taking 27 (6d8) cold damage on a failed save, or half as much damage on a successful one.

Air Slash. Cryovain beats his mighty wings. Each creature within 10 feet of the him must succeed on a DC 15 Dexterity saving throw or take 13 (2d6 + 4) bludgeoning damage and be knocked prone. Cryovain can then fly up to half its flying speed.

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

Move. Cryovain moves up to half his walking speed.

Claw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit:  13 (2d8 + 4) slashing damage.

Tail Lash. All creatures within 5 feet of Cryovain make a DC 15 Dexterity saving throw. On a failed save, a creature takes 9 (2d4 + 4) bludgeoning damage and is knocked prone. On a successful save, a creature takes half damage and is not knocked prone.

Wing Attack. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 8 (1d8 + 4) bludgeoning damage. The target must make a DC 15 Strength saving throw or be pushed 10 feet away and fall prone.