Swampsnare Trap

The cost line does the discriminating here: this Aura shrinks anything by -5/-3, but only drops to a two-mana rate when the creature it targets already has flying. That encodes a matchup preference directly into the mana math. Pay full price to weaken a ground body you could probably chump anyway, or pay the discount to snipe the evasive threat that black has always struggled to block, with the color's structural weakness priced straight into the spell rather than left to the pilot's judgment. The -3 to toughness reaches into lethal range irrespective of indestructible, since a creature whose toughness hits 0 is put into the graveyard as a state-based action with no destruction event to prevent; the ceiling is high-toughness bodies that cling to a point or two. Being an Aura rather than a sorcery, it carries the friction of its card type: target a creature that leaves the battlefield in response and the spell fails to resolve, and like any targeted removal it fizzles against hexproof or shroud. Where a plain shrink Aura would leave the discount off the card entirely, this one openly rewards you for pointing it at the flier that was going to kill you: an unusually literal way to write a color's blind spot into its removal.