Mana Charity

At the beginning of each-player-that-is-higher-than-you-on-the-leader-board's end step, put a charge counter on Mana Charity for each untapped land that player controls.
Remove a charge counter from Mana Charity: Add one colorless mana to your mana pool. Any player equal to or lower than you on the leaderboard may activate this ability but only during his or her turn before the end step.