Cyclopean Tomb

[2], [Tap]: Put a mire counter on target non-Swamp land. That land is a Swamp for as long as it has a mire counter on it. Activate this ability only during your upkeep.

When Cyclopean Tomb is put into a graveyard from the battlefield, at the beginning of each of your upkeeps for the rest of the game, remove all mire counters from a land that a mire counter was put onto with Cyclopean Tomb but that a mire counter has not been removed from with Cyclopean Tomb.