Infiltrate

Unblockable, distilled to its cheapest possible form: no body attached, no recursion, no rider, just a single blue mana that opens a lane for one turn. The design lineage runs through every "your creature gets through" effect blue has printed, but this one strips away everything except the function, which is what makes it a clean tool for the jobs that need it. It exists to deliver a payload: the equipped beater, the infect creature, the saboteur with a combat-damage trigger you want to fire. The instant speed earns its keep in a narrow window: you can wait until your own combat to read whether the defender leaves blockers up before committing the spell, rather than tipping your hand by casting it at sorcery speed in your main phase. The crucial discipline is that it has to resolve before the Declare Blockers step to do its work; point it during your beginning-of-combat or declare-attackers window, not after the defender has already assigned blocks, because once a creature is blocked, telling it that it can't be blocked changes nothing. The effect also lasts exactly "this turn," so there is no holding it across turns to bluff a crackback; the clock starts and ends in the same combat. The cost of all this is fragility. There is no value built in, so a removal spell in response leaves you down a card with nothing to show for it, rewarding a board that can already close rather than one still assembling. That austerity is the whole pitch: one mana for one mana's worth of effect is the honest rate, and the absence of any extra clause is the point.