Light 'Em Up

Casualty is the mechanic that lets a spell eat a body to duplicate itself, and here it is bolted onto a small piece of removal. The base rate puts two damage on a single creature or planeswalker: a trade a red deck makes without ceremony. Sacrifice a creature with power two or greater as you cast, though, and the spell copies, so the same two mana answer twice. What keeps that from being a free two-for-one is the cost of the copy: the fodder is a creature you already control, and it has to be worth more as a second kill than as a blocker left on the battlefield. You need expendable power sitting there before the spell is even worth casting at full value. The retarget is optional (the trigger says you may pick a new target), so this is genuinely two spells resolving one after another: aim both at the same threat for four damage stacked onto one problem, or split them across the board when you have two. That range is the appeal, from a clean single removal to a double answer, with the sacrifice priced as a real decision rather than a rubber stamp. It is casualty at its most transactional, converting a body you were about to lose anyway into a second removal spell.