Smoky Lounge // Misty Salon (Duskmourn: House of Horror 235) - Uncommon Magic: The Gathering Card

At the beginning of your first main phase, add . Spend this mana only to cast Room spells and unlock doors.
(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.)