Earthshatter

You slam the ground in front of you, sundering the ground in two. Each creature in a 15-foot cube originating from you must make a Dex save (DC 8+Strength Modifier+Proficiency). On failure, a creature take 2d8 bludgeoning damage and is knocked prone. On success, the creature takes half damage and isn't knocked prone. Each additional slam used after the first causes one point of exhaustion. Also if the terrain is breakable, it is destroyed and becomes difficult terrain.