Curtain of Light

The defensive answer to evasion, which is a much rarer thing than the offensive answer. Most ways to deal with an unblockable creature involve killing it or bouncing it; this one simply revokes the keyword for a single combat by declaring the creature blocked after the fact. The trick is that "blocked" and "actually blocked by something" are different game states: a creature flagged as blocked with no blocker assigned to it deals no combat damage unless it has trample, so the threat connects with nothing. The timing window is the whole engine. The spell can only be cast after blockers are declared, which means the attacking player has already committed to the swing and chosen targets before it resolves, leaving no room to redirect or reroute the damage. Used on the right target, it turns the one creature you cannot otherwise stop into a swing for zero. The cantrip is what keeps the slot from going dead when the opponent has no evasion to punish: the card replaces itself, so holding it up costs only the mana, never the card. The design is narrow by intent, an answer keyed to a specific kind of threat rather than a general-purpose Fog, and it belongs to the family of combat tricks that solve a creature without ever touching its stats or removing it from the battlefield.