Take into Custody

A Frost Breath that declines the second target, sold instead for a single blue mana. The trade is the whole calculus: spend less, get a cleaner tempo swing against one creature's clock. The real value sits in the deferred untap, not the tap itself, since the creature stays tapped through its controller's next untap step. Cast it end-of-turn on an untapped blocker and you clear the lane for your own attack the following turn; aim it at a creature that relies on being untapped (a would-be blocker, an attacker mid-swing, a vigilance-less threat you want off defense) and you buy a full turn of that creature doing nothing. What it does not do is shut off a costly activated ability that pays with mana or a sacrifice: tapping only silences abilities that need the creature untapped or ask for a tap in their cost, so this is a tempo lever, not a lockdown. At instant speed and one mana it fills the role the lightest tap-down effects have always filled: not removal, but a borrowed turn, paid back in initiative rather than card advantage. The honesty in the design is that the creature comes back fully functional two turns from now; you are renting tempo, not buying it, and the rent comes due against any deck patient enough to wait you out. That ceiling is exactly why this kind of effect lives at common and stays there: cheap enough to always be castable, narrow enough to never warp a board.