Lethargy Trap

Greed is the trigger. This is a punishment dressed as a fog: as long as your opponent keeps a measured board, the spell costs four and rarely earns the slot, but the moment three or more creatures turn sideways, the cost collapses to a single blue and the swarm pays for your discount. The clause that defines its lane is the minus-three to power rather than toughness: nothing dies, so it blunts rather than sweeps. Against a wide deck of one- and two-power attackers the arithmetic is ugly for the aggressor, with small creatures zeroed out for the turn and a lethal swing reduced to a whiff; against two fat threats it shaves a few points and leaves them connecting, and the alternative cost never even unlocks. The reactive design is precise about its window. It wants to be held until the declare-attackers step, after the opponent has committed their entire team and locked in the attack but before damage resolves, the exact moment when the bait has already been taken and the price is cheapest. Hold it earlier and you are paying full freight for a weaker effect; hold it correctly and you spend one mana to erase a turn of pressure. The narrowness is intentional: it does nothing against restraint and everything against overcommitment, an answer that scales inversely to how badly you needed it.