Reciprocate

Retribution by construction: this fires only after a creature has already bloodied you, which turns a one-mana removal spell into a punishment for the attack rather than a proactive answer. It does nothing on an empty board, nothing against a creature held back, nothing against an attacker pointed at your planeswalker or your teammate. You have to take the hit first. What you get for accepting that narrowness is rare at this price: it exiles rather than destroys, so indestructibility, regeneration, and death triggers all go ignored, and it carries no toughness ceiling, so the fattest beater dies the same as the smallest token. The design lives in a recognizable white tradition of gated removal, answers that fire only once the opponent has committed: spells that hit only attackers or blockers, justice meted out after the crime. The timing is unforgiving in a way the cheap rate disguises. The legal window is exactly the turn the damage lands and no later, so a creature that hits you during the opponent's turn must be exiled before that turn ends; once priority passes back to you, it has dealt no damage to you this turn and is no longer a target. That cleanup-step deadline, not the mana, is the real cost. It asks you to absorb a blow and collect inside the same breath.