Realms of Uncertainty

When Realms of Uncertainty enters the battlefield, each player exiles all lands he or she controls in a face-down pile, shuffles that pile, then puts all cards in that pile onto the battlefield face down as lands under his or her control. (He or she can't look at them.)
All face-down lands have "{3}: Turn this permanent face up." and "{t}: Add {c} to your mana pool."