Master Transmuter

The bounce-and-replay loop is the whole engine: tap, pay a blue, return an artifact you control to hand, and put an artifact from your hand onto the battlefield. The trick is that it sidesteps casting cost entirely. Whatever you drop arrives for the activation price, not its own, which turns a backbreaking artifact (a Mindslaver, a Blightsteel Colossus, anything with a brutal mana value) into a one-blue cheat. Because returning the artifact is part of the cost, it is already in your hand when the ability resolves, so you can put that very same artifact straight back down: a clean way to re-trigger an enters-the-battlefield effect, or to flicker a permanent out of a removal spell's path and redeploy it the moment the dust settles. Protecting a board and building one cost the same activation. Two restrictions keep it honest. It taps, so the loop is one activation per turn without an untapper. And it pulls from hand rather than the graveyard, so the engine is only as deep as the artifacts you can keep picking up and setting back down. The 1/2 body is fragile and beside the point: this is not a creature that fights but a color-light, instant-speed artifact-deployment valve that resets every turn. It sits squarely in blue's tradition of cheating artifacts onto the battlefield, the Tinker and Arcum Dagsson line, trading their raw explosiveness for something recurring, defensive, and repeatable.