Furnace Brood

The whole reason this elemental exists is the repeatable button stapled to its body, and that button is pure regeneration hate. It was printed into an era when regeneration was a load-bearing defensive keyword: green and black fielded walls and creatures that shrugged off removal by tapping for a shield, and decks leaning on those creatures could be genuinely hard to break through. The ability answers that directly, turning each red mana into a regeneration-stripping shot so a single combat or removal spell actually sticks. The design is narrow by intent: it does nothing against a board with no regenerators, and it asks you to hold the red to fire at the right moment rather than committing it up front. That timing matters, because "can't be regenerated this turn" only does work when you pair it with the damage or removal that follows. As regeneration faded from the game's design vocabulary (Wizards steadily moved its anti-removal toughness onto indestructible, ward, and protection instead), cards built to police it lost the world they were policing. What remains is a clean artifact of a more answer-dense age: a body that fights on the board and a button that exists solely to switch off another player's plan A.