Pitfall Trap

The bargain is structural: overextend a lone attacker, and the white mana you held back becomes a one-mana removal spell that erases it before damage. The trap mechanic asks the opponent to walk into a condition, and this one keys on the simplest tell in combat, the single attacker. Send exactly one creature into the red zone and the discount unlocks; spread the offense across two or more bodies and it evaporates, leaving you a flat three-mana destroy effect that any white deck could run without the gimmick. That fork is the whole design: the trap rewards a defender who reads an aggressor committing a solitary threat, and quietly fails against an aggressor who knows to widen the board. The "without flying" rider is the other restriction, narrowing the answer to ground creatures and keeping it off the evasive threats white most wants help against. It is conditional removal dressed as a tempo blowout, and the price of the blowout is that the opponent decides whether you ever get to pay it.