Piercing Light

The restriction on the target is the whole design: this can only point at a creature that has committed to combat, which is exactly the moment a two-damage instant does the most work for the least mana. It cannot pick off a mana dork on turn one or answer a threat sitting back on defense; it waits for the attack step or the block, then trades for a single white mana while smoothing the next draw. That combat-only clause is what keeps a one-mana removal instant from being oppressively flexible: it is a tempo tool priced for the exact window it serves, not a catch-all answer to everything white cannot otherwise touch. Because the spell needs a legal attacking or blocking target to be cast at all, the scry is not a fallback for dead turns; it rides along on a kill you were already making, sharpening what would otherwise be a plain trade of two damage for one mana into a play that also fixes a topdeck. White has always paid for its cheap combat interaction with a timing constraint, and this is that bargain in miniature: raw power surrendered for a restriction on when the spell can be cast, the trade that lets white run efficient removal without reaching past its color-pie limits into noncombat threats.