World Enchantment At the beginning of your upkeep, sacrifice Koskun Falls unless you tap an untapped creature you control. Creatures can't attack you unless their controller pays {2} for each creature he or she controls that's attacking you.1
2/1/2007: In the Two-Headed Giant format, you still only have to pay once per creature.
10/1/2008: This has the supertype world. This supertype is similar to legendary. The difference is that when a world permanent enters the battlefield, any world permanents that were already on the battlefield are put into their owners' graveyards. This is a state-based action called the "world rule." The new world permanent stays on the battlefield. If two world permanents enter the battlefield at the same time, they're both put into their owners' graveyards.