Leonin Bladetrap

Flash is what converts a fragile artifact into an ambush, but the ambush has a price tag: cast it () before combat and the activation () waits until attackers are declared, so the player who wants the surprise blowout is holding five mana open across the turn. Done that way, the lands against creatures already committed to the swing, and two damage washes over every grounded attacker at once. The asymmetry lives in the sacrifice ability rather than in any color: only attacking creatures take the hit, so the defender's own board stays untouched no matter how it's built, and the flying clause carves out the air. That makes it an answer to the exact problem colorless decks have always had trouble with: a wide ground swarm, a token flood, a horde of small bodies arriving faster than spot removal can keep up. The cost on top of casting means it is never free, but the payoff scales with the opponent's overextension instead of your own resources. It asks nothing of your deck's identity (no creatures to feed it, no graveyard to fuel it), only that you keep mana up and let an aggressor walk in. The result is a tax on overreach rather than a board reset: it punishes the player who oversteps on the ground, charging for reach instead of presence.