Spring-Loaded Sawblades // Bladewheel Chariot

Five damage at flash speed, priced by a single condition: the target has to already be tapped. That constraint is the entire cost, and it turns the front face into a punisher rather than a proactive answer. You cannot point it at a fresh creature on an empty board; you wait for the opening, a creature that committed to an attack, a mana dork tapped for value, a Vehicle that already crewed in. Flash it during an opponent's combat and their attack step becomes the kill window, since the damage fires on entry and needs nothing else from you. For a colorless artifact this cheap, killing something with five toughness is well past what removal at this rate usually reaches.

Then craft converts the spent answer into a threat. Exiling the sawblades alongside another artifact returns them as Bladewheel Chariot, and the Vehicle is where the design commits: it can crew for a single point of power, or it can animate itself by tapping two other artifacts, so an artifact-dense board attacks without ever exposing a creature to the crew step. That self-crewing line is the one that carries a shell built to feed it, sidestepping the usual Vehicle liability of leaving a real body tapped and vulnerable. The two halves look like unrelated effects bolted to a transform, but the through-line is artifact commitment: it snipes a tapped attacker on the way in, then leans on the artifacts around it to swing the survivor home.