When Realm Razer enters the battlefield, exile all lands. When Realm Razer leaves the battlefield, return the exiled cards to the battlefield tapped under their owners' control.
The behemoth roared, and the world was blasted free of empires and tyrants.
Official Rulings for Realm Razer
10/1/2008 : If Realm Razer leaves the battlefield before its first ability has resolved, its second ability will trigger and do nothing. Then its first ability will resolve and exile all lands forever.