Cube Shot

You conjure a cube of sphere-metal in your hand, and shoot it at a creature within range. Make a ranged spell attack. On a hit, the target takes 1d8 bludgeoning damage and must succeed on a Strength saving throw or fall prone. If you roll a 20 on the attack roll, and the target fails the saving throw by 10 or more, then it instead is knocked unconscious. The damage increases by 1d8 at 5th(2d8 total), 11th(3d8 total), and 17th(4d8 total) level.