(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)
At the beginning of your upkeep, exile the top card of your library. You may play that card this turn.
//
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)
Once each turn, you may pay
rather than pay the mana cost for a spell you cast from exile.
