Ringing Strike Mastery
Blue's answer to a threat has usually been to unmake it: bounce it, counter it, steal it. This works narrower and slower. It taps the creature as it enters and then withholds the untap step, the classic Icy Manipulator effect rendered permanent and one-sided, folded into a single-mana Aura. The escape hatch is the wrinkle: enchanted creatures gain their own untap ability, so it functions as a tax rather than a hard lock. The opponent can always free the creature; they simply have to pay five mana to do it, turn after turn, which is rarely a trade worth making on the back of a beater. That is the design choice at work: the controller retains agency, and the card cares more about buying tempo and stalling a clock than shutting a threat off forever. Because the tap happens on entry, even vigilance does not slip the leash: a vigilant attacker still gets pinned down until the tax is paid, since the problem is the missing untap step, not the swing. What it neutralizes is anything whose value lives in repeated untapping: a mana creature, a tapper, an attacker the controller cannot afford to let loose. It does nothing about abilities that need no tapping at all. A soft answer, priced like a cantrip, that turns off a permanent's rhythm instead of removing it.
