Monkey Cage

A loaded trap with the safety filed off. The cage sits idle, waiting, then springs the moment any creature enters the battlefield under any control, sacrificing itself to spit out 2/2 green Monkeys equal to that creature's mana value. That phrase, "any control," is the whole strange engine: the artifact has no allegiance and no discretion, so an opponent's bomb fills your side of the board, and an opponent can defuse it just as cheaply by playing a one-drop and watching the cage cash out for a single Monkey. The reward scales with size (a fatty entering hands you a swarm) but the trigger arrives on whatever schedule the table decides, which is to say not yours. The intended line is to engineer the entry deliberately: blink something large, reanimate something larger, sequence the trip so the Monkeys land where they should. That makes a five-mana artifact the back half of a two-card combination rather than a card that pulls its own weight, a demand most decks have never been willing to meet. It is a relic of an older design instinct, when artifacts keyed off the entire table's creatures instead of only their controller's, and the chasm between the ceiling and the floor is precisely the appeal: the cage will pay out spectacularly, but only for a player who can dictate which creature trips it, and dictating that is exactly what the card declines to do on its own.