Nim Devourer

A recursion engine built to feed itself rather than to attack. The graveyard ability reads as resilience: pay two black, bring the Zombie back during your upkeep, and the board persists. But the sacrifice clause turns that loop into a conversion machine. Each return demands a creature die, which recasts the body as a delivery mechanism for death triggers, sacrifice payoffs, and graveyard fuel that wants creatures pitched repeatedly. The 4/1 frame, growing for each artifact you control, only matters in an artifact-dense shell, which happens to be exactly where the sacrifice fodder tends to live. The upkeep-only restriction is the price that keeps the recursion from becoming a free reanimation valve: you cannot return it at instant speed to ambush a combat step or rebuy it the moment it dies, so the engine grinds only during your upkeep, predictably and on your own schedule. That deliberate slowness is the whole point. It is not a clock you race but a grinding presence that asks for an aristocrats-style board to surround it. The artifact-matters era that produced it gives the power-boost a home, but the card's lasting identity is the trade it offers every upkeep: a creature for a creature, over and over, until the engine runs out of fuel or the triggers close the game.