Cyclopean Tomb {4}
Artifact
{2}, {T}: 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 only during your upkeep.
When this artifact 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 this artifact but that a mire counter has not been removed from with this artifact.
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Cards that do something similar expected a card that isn't here?
Reports become test cases the matcher is graded against before an update ships. Delvefall isn't a chatbot guessing, it compares the printed rules text of every card with plain math, and examples like yours decide which differences should count.