The Rose Codex is a special book, of which only 3 copies are known to exist though the whereabouts of all but one are unknown. One copy is known to reside within The Vault for Vident Obscura, it was found on Soteria during the initial explorations of the surface while Nysa was under construction. The location and other artifacts surrounding the book indicate that it was previously in the possession of a military organization similar to that of religious fighting groups in the medieval era on Earth, called the Souls Templar.
Contents
The book itself contains all the symbols and instructions on their use for the navigation of the Verum Transitus, it even contains the runes requires to create an entry point to the Transitus or Crossroads. When opening the book it seemingly never runes out of pages containing a physically impossible amount of information inside, given that the Transitus can be used to cross all dimensions of time and space, this makes sense. The language the book is written in seems to be a derivative of Latin, though it is not identical and the runes it describes are in no known language at all.
Writing within the book describes a complicated way to represent not just time and space but realities and how they interconnect with each other.
Pages
To make a copy of a particular map, one need only find the correct page and tear it out. The original page will remain but a sheer of parchment paper will be produced which contains a static map and the runes requires to navigate it. This map will not update, and locations in the Transitus can change over time, meaning it is a temporary map though may last for decades, centuries, or longer.
Properties
Anyone can open the book but it takes years of study to be able to properly understand what is inside, the language is close enough to Latin to study but far enough away so that no direct translation is possible. Those who have studied the writings have said it is one of the most frustrating translations they have encountered finding situations over time where they understand what the writing means but find it difficult to put into other words. It is possible that the writing itself resists translation.
Origin
Myths and legends indicate that the Codex may have been created long after the Transitus itself was created while others indicate that the Codex appeared in the Transitus and was created by the crossroads itself. There are no reliable records of when / where / how the three different volumes were found, though some of the mythology suggests they could have been found in moments of "great need" by who found them.