Fatal Mutation

A removal spell whose timing the opponent controls but whose payoff you guarantee. Hang it on any face-down creature and the destroy trigger waits, dormant and patient, for the controller to commit the mana to turn it up. That moment (the tempo-positive blowout they've been saving) is the exact moment the creature dies, with regeneration ruled off the table. The opponent is left with a genuine dilemma: leave the creature face-down forever and forfeit the value they invested in the face-down state, or flip into the kill. Either way the Aura collects, and for a single black mana it converts an opponent's mechanical engine into a liability. The design lives inside a specific class of mechanic: anything that turns a creature face up. Morph is the obvious target, but the trigger reads on its terms, not on any one keyword's, so manifest, disguise, and cloak all walk into the same trap. That is the elegance and the ceiling both. Against a board with no face-down creatures the enchantment never does its job; it sits on a body without doing anything, waiting for a flip that never comes. This is hate built with surgical specificity, an answer that earns its slot only when the opponent brings the question, and is a dead card the rest of the time.