Sudden Storm

The Frost Breath template at instant speed, with a scry rider stapled on. Where a simple tap effect strands a creature for a single combat, this one does the more durable thing: the targets skip their next untap step entirely, so two attackers (or two blockers) are out of commission for a full turn cycle rather than just one swing. Cast on the opponent's end step, it neutralizes two creatures before your own turn and keeps them tapped through their following turn as well, buying a clean attack and a clean defensive window from a single card. The scry is the concession to card economy: a four-mana tempo trick that left no trace would feel like pure stall, so a single card of selection smooths the price a little without ever refilling your hand. The ceiling is narrow because it reaches only creatures, and only two of them. The floor is real, since the don't-untap clause turns a temporary tap into something closer to soft removal of two threats from the turn that matters most. This is tempo plumbing rather than a marquee card: built to swing one combat-math problem in blue's favor and dig a little deeper while it does.