The Winter Sun

You create a 30-foot-radius sphere of destructive magic within range that engulfs all the creatures inside it. The sphere spreads around corners and penetrates walls less than 10 feet thick. All sufaces are covered in a thin layer of ice. When the sphere appears, each creature inside must make a dexterity saving throw, on a fail they are restrained in ice for the duration of the spell and take 5d10 cold damage, or half as much damage on a successful one.

The sphere is lightly obscured and the ground inside is considered difficult terraign. At the end of your next turn the sphere explodes, and all creatures inside must make a dexterity saving throw. A creature takes 5d8 radiant damage and 5d8 lightning damage on a failed save, or half as much on a successfull one. The explosion destroys all non-magical items that arent being carried or worn. After the explosion, the ice melts and any creature that fails its save is no longer restrained.

At Higher Levels. When you cast this spell using a 9th level spell slot, the initial damage of the freezing ice increases by 1d10, and both the lightning and radiant damage from the explosion increases by 1d8.