The Chronoblade

At the beginning of your upkeep, put a charge counter on The Chronoblade.
{3}, Remove a charge counter: Prevent all combat damage that would be dealt this turn. Untap up to one target land.
{8}, Remove a charge counter: Target a player. Until end of turn. If a source would deal damage to that player, it deals double that damage to that player instead. Tap all lands that player controls.