Shara Ishvalda, The Free

During your upkeep create a boulder artifact
token with "Sacrafice this token: add {1} to your
mana pool," for every colorless land in play.
{5}: Target land is now colorless and its only
ability is "{t}: Add {1} to your mana pool."
{10}{10}: Destroy all colorless lands opponents
control, create a boulder artifact token for every
land removed this way, then all lands apponets
control become colorless and their only ability is
"{t}: Add {1} to your mana pool."