Uchuulon

A self-cloning body whose whole appeal is that the copies keep the engine running. The power counting is closed-loop by design: every token it makes is another Ooze Horror you control, so each copy raises the power of the original and of every sibling at once. Start with a couple of Crabs or Oozes on board and the numbers spiral quickly, because the token isn't a static snapshot; it recalculates its own power off the same board it just grew. That's the mechanical trick worth naming, but the black flavor lives in the end-step trigger. Horrific Symbiosis feeds on opponents' graveyards rather than your own, which pushes the card toward a graveyard-hate role it doesn't advertise: each of your end steps you can pull a reanimation target out of an opponent's graveyard before it can be brought back, and you're rewarded with a body for doing it. The target is narrow (a creature card only, so instants and sorceries in the yard are safe) but the exile drains their resources, not yours, which is an unusual place to root a token-generation engine. It asks for almost nothing to start (no tribal commitment beyond itself, since Uchuulon counts as its own type) and pays off more the wider the graveyards across the table run. Left alone across a few turns, the tokens compound into a board where each individual is a large threat and the collective is larger still, all built out of other players' dead creatures.