Might Makes Right

The Threaten effect with a homework assignment attached. One-shot creature-stealing has almost always lived on cheap spells: take a thing, swing, sacrifice it before it goes home. This trades that flexibility for a recurring engine, and the permanence is the appeal: at the beginning of combat on your turn, for free, it borrows an opponent's creature and hands it to you untapped and hasty, ready to join the attack rather than defend. The catch is the conditional gating the trigger. The ability fires only if you control every creature on the battlefield tied for greatest power, which is stricter than simply having the biggest thing around: if an opponent controls a creature that matches your largest, you no longer control each greatest-power creature and nothing happens. So the gate is a genuine power-count war, not just a size check. That makes this a payoff for a deck already ahead on the board, a trample-and-fatties build or one that has swept the way clear, and it is precisely when you are winning that pace that stealing the opponent's best blocker matters most. The design tension is honest: a recurring steal at six mana with no rider would be oppressive, so the price is that you have to earn the right to use it by dominating the top of the board. Each turn it turns on, the opponent loses their strongest body for a turn and hands you an extra attacker, then gets it back at end of turn, already spent.