Disciple of Bolas

The trigger converts a creature's power into life and cards at the same time, a payoff in two directions that gives this its enduring place in sacrifice strategies. The cost is structural: the sacrifice happens on entry whether you want it to or not, so this is a liability in a deck without bodies and an engine in a deck built to feed it. Because there is no flash, the whole thing happens at sorcery speed, which shapes what good fodder looks like. You are not ambushing combat or saving a creature mid-fight; you are choosing, on your own turn, the moment to cash in something whose power is already inflated or already destined for the bin: a doubled token, a fat trampler that has done its work, a creature you would have sacrificed anyway. Aristocrat decks love it for exactly that reason, turning a death trigger that was always coming into a fistful of cards and a comfortable life cushion. The 2/1 body is almost incidental; you are buying the trigger, and that trigger scales without a ceiling as long as you can find a big enough creature to convert. The uncapped X is what has kept this in the conversation long after most four-mana value creatures faded: it punishes you for not building around it and rewards you lavishly when you do.