Razor-sharp shards of slate flit about you in a lacerating whirlwind until the spell ends. Each creature that starts its turn within 5 feet of you or enters a space within 5 feet of you for the first time on its turn takes 3d8 slashing damage.   When you cast this spell, and as an action on subsequent turns, you can cause slate to fire out from you in a 15-foot cone. Each creature in the area must make a Dexterity saving throw, taking 3d8 slashing damage on a failure, or half as much damage on a success.