Leechridden Swamp

A Swamp that bleeds. The trade is right there in the enters-tapped clause: you accept a turn of tempo loss up front, and in exchange the land becomes a slow drain engine that no creature removal can touch and no board wipe can answer. The black-permanent gate is the price of that immunity. With an empty board the land is just a tapped source of black mana, so it rewards a board of black nonland permanents before it does anything else. That same condition keeps it honest in two-color builds, where you might run several black sources and still never assemble the two permanents needed to switch it on. What makes the activation distinctive is its reach: it hits each opponent rather than one target, scaling the drain across a multiplayer table without ever costing a second card. The effect is small (one life at a time, one activation per untap), but it sits on a basic-typed land, which means it costs you no spell slot and survives anything short of land destruction. This is the lineage of the painless inevitability engine: a permanent that does nothing fast and everything eventually, parked in a slot you were already going to fill. The enters-tapped tax is what pays for stapling a repeatable life-drain onto a Swamp at no card cost.