Argent Sphinx

The metalcraft payoff is a self-removal blink, a stranger animal than the flying body suggests. For a single blue mana, the sphinx exiles itself and slips back at the next end step, so it dodges any sorcery-speed removal aimed at it, ducks a board wipe with the right timing, and walks back through a combat step it would rather not survive in. The condition is the cost: you need three or more artifacts on the battlefield even to activate the ability, so the protection is dead in a deck that has not committed to the artifact count metalcraft demands. That gating is what keeps a four-power evader with built-in survival from being oppressive. Without metalcraft online it is a 4/3 flier whose escape hatch is bolted shut; with three artifacts down it is a clock that is hard to answer at sorcery speed, since the blink is only live once the creature is already on the battlefield (an activated ability the sphinx cannot use while it is still a spell, which leaves a counterspell as the clean answer before it ever lands). Once it resolves, though, the window opens: exile in response to a targeted removal spell, return after the turn's interaction has cleared. It belongs to the line of artifact-leaning blue beaters that treat your permanent count as a resource rather than incidental clutter, and that exile-and-return window is the entire reason the activation is priced at a single mana.