Blood Lust

Berserk in red, with the math reorganized. The white-bordered cousin asks you to double power and trade the creature's life for the swing; here, the deal is structural rather than lethal. Whatever the target, it gets the full +4 power: against a five-toughness body the rate is clean, +4/-4 leaving a one-toughness creature and a much bigger threat, and against anything smaller the toughness penalty scales precisely to leave the creature at 1. That floor is the design tell. This is a combat trick that refuses to kill the creature it targets, no matter how small. The spell itself never reduces the creature below 1 toughness, so it survives the trick at 1 to deliver the full +4, but you also cannot use it as a sacrifice-trigger enabler or a self-kill for a death payoff. The constraint is doing real work: a pure damage-amplifier with a built-in floor, designed in an era when red's combat math was still being calibrated and the question of how much damage a two-mana instant could add to a single attack was genuinely open. The answer was four, always four, with the toughness reduction sculpted around it so the body always survives to carry the swing. Nothing printed since has quite copied the "leaves it at 1" clause; the card sits alone, more a one-off experiment than a template anyone returned to.