A blade of wind flies from your outstretched hands in a straight line up to 15 feet in a direction you choose. If the blade would strike a creature, it must make a Dexterity saving throw. On a failed save, the target takes 1d8 slashing damage and then the spell ends. This spell deals an additional 1d8 slashing damage when you reach 5th level (2d8), 11th level (3d8) and 17th level (4d8).