Predatory Urge

Most fight effects are one-shot spells that resolve and disappear; this one bolts the mechanic onto a permanent, turning a single creature into a repeatable trading engine. The aura grants its host a tap ability that points two creatures at each other, each dealing damage equal to its power, and the only cost is the tap itself, so the limiting factor is whether the host survives each exchange to untap and do it again. That makes the math the entire game: enchant something with high power and high toughness and you have a creature that picks off smaller threats turn after turn without ever committing to attacks, the enchanted body soaking whatever it targets. Where a fight spell asks you to win one combat calculation on the spot, this asks you to build a body durable enough to keep winning them. The friction is the tap: the ability needs a host already free of summoning sickness, the aura sits on one creature, and it hands an opponent two cards for one if they kill the host in response to an activation or remove it on their own turn. Deathtouch is the obvious pairing, making a tapper that trades up against anything regardless of size, but even without it the design captures something fight spells cannot: a standing threat of removal that lives on the battlefield, taxing every creature an opponent commits while the enchanted body holds the board.