Kethek, Crucible Goliath

The engine works downward, and that's the whole tension. Each end step you feed it a creature, and it digs for a nonlegendary body of strictly lower mana value than what you sacrificed, so the chain can only descend: a five-drop fetches a four, a four fetches a three, and eventually you bottom out on the one-drops. That descending-value clause is what pays for a free, repeatable put-onto-the-battlefield trigger that most reanimation designs gate behind a spell or a mana cost. It rewards a curve built around expensive fodder and cheap payoffs, and it punishes the flat aristocrats deck that runs a wall of two-drops with nothing meaningfully smaller to hit. The reveal-until clause matters too: this is not selective tutoring but a dig that puts the rest on the bottom in random order, so it thins toward your creatures while quietly burying your removal and lands until you reshuffle. What distinguishes it from a standard sacrifice-value creature is that the sacrifice and the payoff live in the same body at end step, sidestepping the usual pairing of a sac outlet with a separate recursion engine. The cost is the descending ladder and the commitment to a top-heavy creature base worth walking down.