Mutant's Prey

The price of a single green mana is paid in a deckbuilding clause rather than a higher cost: the creature you point has to already wear a +1/+1 counter. That restriction turns a generic fight spell into a payoff that only fires inside a counters shell, where the mechanics that pile up marks have already buffed the team before this card asks anything. The reward for that narrowness is a rate green rarely gets on its removal: one mana, at instant speed, to send a reinforced creature at something an opponent controls. Most green fight effects soften the mechanic's built-in risk (the chance your creature takes a fatal swing back) by stapling the ability to a body, so you keep a creature even if the trade goes wrong. This one declines that hedge and exists purely as the instant. The bet is that a counter-laden deck has already won the power-toughness race before the fight is declared, so the return damage rarely lands hard enough to matter; the +1/+1 prerequisite is the same thing that neutralizes the usual cost of fighting. Instant speed is where it earns its keep beyond the rate: held up after blocks, it can ambush an attacker, and in response to an opponent's removal it lets a doomed creature trade up on its way out (the fight does not save it from the removal, but it cashes the creature in before it dies). It is fight stripped to its leanest form, sold to the one archetype that pre-pays the downside.