Lodestone Myr

The pump cost is the whole proposition: not mana, not life, but the tap of an artifact, which ties this creature's size directly to how committed you are to the metal. Each artifact you tap is a click on the dial, and trample is what converts those clicks into damage that does not get chumped away by a single blocker. This addresses the recurring artifact-deck problem of a wide, tapped-out board that does nothing on offense: here, the same permanents that build your engine double as ammunition for a single threat. The catch is real and self-limiting. Every artifact spent pumping is one not producing mana or pressing its own ability that turn, and a sweeper that kills the Myr wastes the entire investment. It is a payoff card built to reward the one thing an artifact-saturated board is already doing, which makes it less a build-around than a natural top-end for a deck that fills itself with cheap metal and Myr.