Room cards have two card faces with a shared type line on a single card. The characteristics of the door you didn't cast are ignored while the spell is on the stack.
Funeral Room // Awakening Hall
Any time you have priority during a main phase of your turn and the stack is empty, you may pay the mana cost of a locked door (also called its "unlock cost"). That door becomes unlocked. This is a special action. It doesn't use the stack and can't be responded to.
To cast a Room spell, choose a half (or "door") to cast. There's no way to cast both halves of a Room card. When the Room spell resolves, the corresponding door becomes unlocked as the Room enters.
Magic: The Gathering · ™ & © Wizards of the Coast · Illus. Alexandre Chaudret
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