Archfiend of the Dross

Six power of flying for four mana is a rate black aggro would normally have to fight to earn, and the payoff hanging off it turns board attrition into a punishment: every time an opponent's creature dies, its controller loses two life. The price is the oil-counter clock. Four upkeeps to close the game, or the card closes it on you. That is the devil's-bargain logic in its purest form: a body that overperforms because it arrives with a self-imposed death sentence, the same trade Phyrexian mana runs on elsewhere. What keeps the clock from being a flat drawback is that oil is a shared currency in this line of designs, and proliferate adds counters back. Proliferate lives in black's neighborhood, so the timer built to punish you can be reset by the same colors that want to cast the card. Left naked, you are racing yourself, forced to convert four turns into lethal before the last counter comes off. Support it with a single proliferate source and the drawback quietly evaporates, leaving a 6/6 flier that doubles as an attrition tax: the effect only bites the opponent, so any removal-heavy grind, any chump-blocking wall, any sacrifice fodder they run bleeds them out one death at a time while your own board stays untouched. The question it poses is whether you can build fast enough to justify the body, or patient enough to keep the counter alive. Either answer is a different deck.