Aegir's Wave

You slam your foot or fists on the ground and radiate storm energy. Each creature in a 20 feet radius makes a Con saving throw. On a failed save, target takes 4d8 Thunder and 4d8 cold damage and are knocked prone. On a success, target takes half as much damage and isn't knocked prone.

At Higher Levels. When you cast this spell using a spell slot of 6th level or higher, the thunder and cold damage both increase by 1d8 for each slot level above 5th.