Heartfire

In Commander, Heartfire earns its slot in aristocrats and sacrifice-value decks where creatures are already dying for profit — the damage converts a Reassembling Skeleton or a token into a removal spell or reach to close out a game. Outside that niche it's too conditional; most Commander tables demand interaction that doesn't require a body on board. In Pauper it competes in aggressive red builds where cheap sacrificeable creatures are plentiful, and the instant speed occasionally matters for combat tricks. Modern and Legacy have enough redundancy in burn and combo that Heartfire rarely sees serious play, though it finds occasional fringe use in sacrifice synergy lists. Pioneer is the most hospitable non-Commander 60-card home given the format's lower power ceiling and accessible sacrifice enablers.