Deadeye Plunderers

A Pirate that reads as an engine but is really a threshold: the body grows with every artifact you already control, and the activated ability lets it manufacture more of that fuel on demand. The trap is treating those two halves as a loop. They are not. The Treasures the ability prints count toward the +1/+1 buff only while they sit on the battlefield, so cashing one in for mana costs a point of power and returns just one of the four mana the next activation demands. The card wants you to hoard, not spend: every Treasure left unbroken is another point of power, and the deck that pays it off is one that can make artifacts without eating into the creature's size. That tension between banking mana as board presence and spending it as ramp is the whole design. The activation is deliberately steep, keeping the growth incremental so the 3/3 base cannot spiral on its own steam; the artifacts have to come from elsewhere. As a payoff for a shell already invested in producing artifacts or Treasures, it doubles as both the thing the engine pumps and a slow source of the tokens that pump it, provided you have the discipline to leave them alone.