When Borderland Explorer enters the battlefield, each player may discard a card. Each player who discarded a card this way may search their library for a basic land card, reveal it, put it into their hand, then shuffle their library.
8/23/2016 Players decide whether or not they’re discarding a card in turn order. Each player will know if previous players are discarding, but not what they are discarding. All cards to be discarded are set aside, then revealed and discarded simultaneously. Similarly, all basic land cards searched for are set aside, then revealed simultaneously.