Yuffie, Materia Hunter

Ninjutsu has always been an aggression-tax mechanic: you trade a connecting attacker for a bigger threat and its enters-the-battlefield payload, dropping the ninja tapped and attacking so the swap costs you no tempo. Most ninjas cash that window for card advantage or extra damage. This one cashes it for larceny. The trigger seizes control of a target noncreature artifact and keeps it under your command only while the ninja stays on the board, which turns a single unblocked hit into a theft engine: mana rocks, Signets, keyrune-style utility, whatever your opponents have leaned on gets pointed back at them. That leash is the pressure valve. The stolen artifact is borrowed, not destroyed, so the whole plan lives and dies with a 3/3 that arrives in the red zone and can be answered on the crackback. The rider that follows (attaching an Equipment you already control) folds a second axis into the same trigger, letting a threat that keeps connecting keep growing, which matters because Ninjutsu wants a creature that gets through more than once. The Materia framing is doing real work here: this is a design about acquiring other people's tools rather than out-carding them, and it asks you to build a board that forces damage through rather than a pile of value spells. The theft is temporary, the tempo is not, and the two together define how the card wants to be played.