"It is not protected," Danielle said, looking at the door. This is the door mention in words scribbled behind the book; behind the door is a room that teleportation formation which could take us to any room in the tower.
From the herb halls to the training room, the only places it could not take in the office of the master of this tower.
Click!
I opened the door, and it opened with a click and on the other side is a small room in which the spatial formation is carved. The formation is undamaged and could be used, but scribbled notes on the book said that it could be used by one person, only one time.
Other people would also be able to use it only once; if they tried to use it again, the formation would not be activated.