Shackle Slinger

Blue rarely gets a repeatable tapper that scales past the first trigger, and this one solves that by folding stun counters into the payoff. The trigger keys off casting your second spell each turn, which nudges you toward the low-curve, spell-dense builds where tapping down a blocker or an attacker every turn is both cheap to enable and quietly punishing. The clever part is what happens when the target is already tapped: instead of wasting the effect, it converts to a stun counter, meaning a creature that's tapped when you fire the trigger again stays down instead of simply untapping. Over a few turns that turns a 3/2 body into a soft prison, keeping the opponent's best creatures off balance without ever spending a card on it. This is a tempo engine dressed as a soldier, and the stun counter is why it outlasts the one-shot tappers of earlier eras: those effects reset every untap step, while this one compounds and refuses to give the untap back. The constraint that keeps it fair is the reach of a single target plus the second-spell requirement, so it rewards a hand that keeps flowing rather than one that dumps its mana in a single big play. Left unanswered, it does the work of a removal spell one creature at a time, indefinitely.