Deadly Precision

The single black mana is the bait; the additional cost is the whole transaction. Unconditional destroy-target-creature at one mana has always been priced somewhere, and this design puts the price in a place the caster controls rather than the deckbuilder. You either pay four generic (turning it into a five-mana Murder that is happy to sit late-game) or you feed it an artifact or a creature, which is where the card stops being removal and starts being an engine input. That sacrifice clause is the interesting axis: it is a removal spell that willingly pays in bodies, so in a deck that wants creatures dying anyway (a token board, a graveyard shell, an aristocrats loop that cares about the leaving), the "cost" is a second effect you were already trying to generate. The additional-cost structure is doing double duty as a fixed price and as a synergy hook, and which one it is depends entirely on the shell around it. The trade-off keeps the rate honest: with nothing to sacrifice you are paying full retail, so the card punishes an empty board and rewards a cluttered one. That inversion (removal that gets cheaper the more you have already committed) is a cleaner statement of the black-sacrifice value proposition than most spells that try to bolt the theme on, because here the theme is the mana cost.