Wave of Hell

With both the sides of heat and frost merged together, a tidal wave of cold fire rains down onto the enemies caught in its path, all creatures in its path take 4d6 Cold and 4d6 Fire damage, and must make a Dexterity Saving Throw. On a successful save, the targets take half damage. On a failed save, the targets take full damage.

At Higher Levels: When cast with a 4th level spell slot or higher, each damage die increases by one