Elitzur's Debilitating Blast

You hurl a mote of force at a creature or object within range. Make a ranged spell attack against the target. On a hit, the target takes 1d8 force damage. If the creature would be taken to zero hit points, it instead is knocked unconscious as per the sleep spell at 1 hit point. 

This spell's damage increases by 1d8 when you reach 5th level (2d8), 11th level (3d8), and 17th level (4d8) .