Breath of the North

A blast of cold air erupts from your hands. Each creature in a 30-foot cube must make a dexterity saving throw. A creature takes 4d8 cold damage on a failed save, or half as much damage on a successful one. If you fail, then you will be incased in ice and take 2d8 cold damage every turn. Any creatures incased in the ice cannot make any actions or bonus actions. To escape the ice a creature from the outside must break it open. The ice has an AC of 15.       

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the damage increases by 1d8 for each slot level above 4th.