Dissension in the Ranks

The double restriction in the targeting clause is where this lives: both creatures must already be declared as blockers before you can resolve anything. That single condition converts a fight spell into a combat-step ambush rather than a board-control tool. An attacker is off-limits; so is a creature sitting untapped on defense, or a blocker you'd like to clear before your opponent commits. The spell fires only after they've thrown bodies in front of your swing, and then it makes those defenders turn on each other. Note what it does not accomplish: a blocked creature stays blocked even after its blocker dies, so unless your attacker has trample, this is not a way to force damage through. It is a way to trade two of their defenders for none of your own, cashing a cluttered block into a single removal event. Five mana is steep for a conditional fight, which is the price the effect pays for that ceiling. Instant speed is the entire mechanism, because the window is razor-thin: declare attacks, let blocks happen, resolve the fight before combat damage. Most fight spells hand the controlling player the matchup at leisure; this one gives you the fight only after the opponent has chosen how to defend, making it a read on their combat math as much as a removal spell. Demanding to set up, and inert in hand the rest of the time.