The one-way door allows players to enter, but not return through it. This is because matter can only proceed in one direction within the door frame. Moving backwards while half-way through the door would feel like trying to push your body through a wall.

Once you’re on the other side, the door may not exist or the open space may feel like a solid wall. You may or may not be able to see and hear your allies on the other side and the exit may not be in the same location where the entrance was.

Once the effect of this door is known, the party may wish to voluntarily split up into two groups, assuming at least 1 person remains on the other side.

This trap is similar to the One-Use Door.