At the beginning of each opponent's upkeep, exile all cards from your hand face down. At the beginning of your upkeep, return all cards you own exiled with Bottled Cloister to your hand, then draw a card.
2006-02-01
Errata'd to make it clear that only the cards you own go into your hand, so if you somehow gain control of the Cloister, your opponent's cards won't go to your hand.