(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.)
You may play lands from your graveyard.
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(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.)
When you unlock this door, you may cast spells from your graveyard this turn, and if a card would be put into your graveyard from anywhere this turn, exile it instead.