Nirkana Revenant

Mana-doublers that touch lands sit in a delicate corner of design: ramp scales nonlinearly, so a creature that doubles every Swamp in a mono-black deck hands you acceleration and a payoff stapled into one body. Caged Sun and Crypt Ghast double black mana too, but they leave you to find somewhere to spend it. Here the +1/+1 ability is the sink that closes the loop. The flood of black mana the first ability creates has nowhere better to go than back into the same body, so a 4/4 becomes a clock that grows by the entire surplus of a developed mana base every turn. The Shade subtype is the genre, and the genre's premise (a creature that converts mana into power at instant speed) is exactly what a Swamp-doubler was built to feed. The two abilities read as a single closed system rather than two effects sharing a card: the more land you commit to it, the faster both halves accelerate, and the same untapped Swamps threatening a lethal pump are also the ones funding the rest of your turn. It functions less like a ramp creature and more like a self-contained engine, and the only thing it asks of a list is Swamp count: the higher the number, the harder both halves of the card hit.