Throat Slitter

Ninja design lives and dies on the connect: the body is irrelevant, but the trigger fires the moment unblocked damage lands, and this one converts a successful sneak into the death of the biggest nonblack threat across the table. The ninjutsu cost is the lever that makes it work. By bouncing an unblocked attacker after blocks are declared, you swap a creature that already broke through for one whose entire purpose is to punish that opening, and you do it at instant speed during the combat step, after your opponent has committed to a board they thought was safe. That timing is the whole trick: the destroy clause reads like a slow midrange tax, but ninjutsu front-loads it onto a combat where the defender's blocks are already locked. The nonblack restriction is the line drawn around it, keeping the effect from cannibalizing the mirror and quietly pointing it at exactly the green and white fatties it was built to cut down. It is removal that has to be earned through the combat math rather than pointed from the hand, which is both its ceiling and its limit: when the attack connects it is a two-for-one tempo swing, and when it does not it is a 2/2 sitting in hand waiting for another opening.