Unlocking a door

Unlock a door is a special action used on Room cards, introduced in Duskmourn: House of Horror. Unlocking a door changes its state from locked to unlocked.
==Description==
When a room enters the battlefield, its doors (halves) are initially locked. If it was cast, the door of the half that was cast immediately becomes unlocked when it enters the battlefield. As a sorcery, the mana cost of a locked door can be paid to unlock it. Unlocking a door this way is a special action: it doesn't use the stack and can't be responded to.
When a door is unlocked, it gains the designation of "left half unlocked" (for the left side of the card) or "right half unlocked" (for the right side). If a Room has both designations, it is considered fully unlocked.
==Rules==
==Rulings==
*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.
*An ability that triggers "when you unlock this door" triggers when that door becomes unlocked. This can happen one of two ways: (1) the door becomes unlocked on the battlefield or (2) the door becomes unlocked as the Room enters the battlefield because you cast the corresponding half. In the latter case, since the door becoming unlocked is what causes the ability to trigger, effects that cause abilities that trigger when a permanent enters to trigger an additional time (such as that of Panharmonicon) won't apply.
*Some abilities allow you to unlock a door of a Room you control. You can't choose to unlock a door that's already unlocked with such an ability. If such an ability requires a target, you can target a Room even if both of its doors are unlocked, but the ability won't do anything when it resolves.
*Some abilities allow you to lock a door of a Room you control. You can't choose to lock a door that's already locked with such an ability. If such an ability requires a target, you can target a Room even if both of its doors are locked, but the ability won't do anything when it resolves.
*Some doors have abilities that trigger whenever you unlock that door and require one or more targets. You can unlock that door even if there would be insufficient legal targets for that triggered ability. The triggered ability won't go on the stack.
*An ability that triggers "whenever you fully unlock a Room" triggers when a door becomes unlocked and the other door of that Room is already unlocked, or when both doors of that Room become unlocked simultaneously.
==Example==
==Gallery==
File:DSK punch card 1.jpg|Duskmourn punch card for "Locked" Doors.
File:DSC punch outs.jpg|Duskmourn Commander punch-outs for Locked Doors.
File:Locked Room MTGO.png|A locked door on Magic Online.
==References==
Category:Miscellaneous mechanics