Aedric's Travelling Doorway

This spell allows the caster to create a magical link between one doorway (subject), and another doorway (target) that the caster is familiar with so long as they are on the same plane of existence. The caster must have seen or touched the other doorway at least once before. For the duration, upon opening the door the caster can see through as though looking through the target doorway, and any creature or material can pass, or be passed, through as though stepping through the doorway, in either direction. The door must remain open for the duration. Closing the door early ends the spell. The spell can only target non-magical doors and cannot be used to gain access to magical doorways such as created by Mordenkainen's Magnificent Mansion.

The caster must specify as part of the casting which direction the doorway will open at the targeted side, i.e., if the target door normally leads to a room, whether the doorway will open into the room, or lead to the exterior of that room.

For the duration of the spell, anyone attempting to open either the subject or target doors from the opposite side finds them stuck and are unable to open them.

By casting the spell on the same subject doorway every day for a year, the spell can be made permanent. Once permanent, the target doorway can be changed by casting the spell on the doorway again. This only changes the target doorway and does not negate the permanence.