Gargantuan Leech

The scaling is the whole pitch here: a 5/5 lifelink body that starts at a printed eight mana and only becomes payable once your Caves have accumulated. What makes the design tick is that it counts Caves in the graveyard as well as on the battlefield, so the discount is durable in a way most cost-reduction is not. A Cave that dies or gets sacrificed keeps working, meaning the reduction ratchets in one direction and never resets when your lands trade or your spent Caves get buried. Lands rarely leave the graveyard, so a deck running a critical mass of them is effectively banking discount as it develops rather than holding it hostage to a fragile board. That inverts the usual tension with lands-matter payoffs, where you want the enablers on the table and the reward asks you to keep them there. This one is content to see them dead. On its own, the printed cost is a non-starter and the card admits as much; it is a payoff piece, not a standalone threat, built to reward a specific land subtype rather than to be splashed for its rate. The lifelink is the finishing touch, turning a body that only shows up in a committed shell into a swing on the life total large enough to matter in the games where you have already done the work.