Coldfireball

A bright streak flashes from your pointing finger to a point you choose within range and then blossoms with a low roar into an explosion of coldfire. Each creature in a 20-foot-radius sphere centered on that point must make a Dexterity saving throw. A target takes 8d6 cold damage on a failed save, or half as much damage on a successful one. This cold damage ignores cold resistance, and creatures immune to cold damage treat their immunity as resistance to cold damage instead.

The coldfire spreads around corners. It ignites flammable objects in the area that aren't being worn or carried. If a creature or a flammable object takes cold damage from the coldfire, the target ignites. Hot fire smothers coldfire; until the target is dealt fire damage, it takes 3 (1d6) cold damage at the start of each of its turns for 1 minute.

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the damage increases by 1d6 for each slot level above 4th.