Mirror Match

The timing restriction is the entire engine: this can only be cast during the declare blockers step, after attackers have committed but before damage. That window is what makes the effect surgical rather than symmetrical. By minting a copy of every creature swinging at you (or your planeswalkers) and assigning each token to block its original, the spell turns an alpha strike into a mirror brawl where every attacker meets an identical body. The defending player effectively trades the opponent's whole offense against itself, then exiles the evidence at end of combat. The genius and the cost both live in the conditional: it does nothing against an empty board and nothing on your own attack, so it sits idle until someone overcommits into you. Against a wide token swarm or a single oversized threat with no evasion edge, the result is a one-sided massacre paid for entirely by the attacker's eagerness. Each token is a copy of the attacker's copiable values, so it brings the same base power, toughness, keywords, and any copiable modifications already on that creature (a deathtouch attacker meets a deathtouch blocker; a trampling beater is matched by a body sized to eat it), though it inherits none of the counters or temporary buffs the original picked up along the way. It is a fog that hits back, a combat blowout that scales to the threat instead of a fixed number, and a reminder that the declare-blockers step is the most underused instant-speed window in the game.