Mole Worms

Tap one of an opponent's lands and it stays down: not destroyed, just frozen, for as long as the worm itself remains tapped. That swap is the entire engine. You spend the worm's tap once to lock a land, then decline to untap the creature on your following untap steps to hold the lock in place; the moment it untaps or dies, the land comes back online. The body brings nothing to combat, so everything rides on that ability, and the cost is steep in its own quiet way: a creature kept tapped to anchor the tax cannot block, cannot attack, and folds to any removal that finds it while it works. That fragility is what makes a repeatable land-lock affordable at all. Unlike Stone Rain or any spell that blows up a land, this leaves the land alive and useless, so the disruption is conditional and reversible rather than permanent. It comes from an era of creatures built to tax rather than kill, an approach Magic largely set aside in favor of cleaner one-shot land destruction before revisiting the tap-down idea much later with permanents that froze things for value. Here, a three-mana creature ships with a single all-consuming job: keep one of an opponent's lands from doing anything at all, for as long as the worm is willing to sit idle.