This is public information.
The Runners make up the most prolific organisation in the city. Consisting mostly of freelance runners who know the city and its books like the back of their hands, and they are the ones that travellers go to when seeking a specific book. After all, when faced with a city-sized library, even the most dedicated loreseeker can have some problems finding what they’re looking for.
The Hermetic Order rules a small but important part of the city known as the Walled Quarter. Here, all the books on magic are concentrated and stored, and none but a member of the Hermetic Order may enter the Walled Quarter on pain of permanent exile from the city. Members of the Order regularly patrol the Quarter which, true to its name, lies behind four great walls.
The Librarium Council rules the City as a whole. Said to be made up of the seven most powerful mages in the world, the Council rarely interfere with the day-to-day affairs of the city, preferring instead to let society sort itself out. The one thing that they actively involve themselves in are matters of land claims. A deed issued by the Council is considered to be inviolate and is the only way one manages to hold down any property in the city.
The Keepers are ghostly figures that wander around the Librarium at all times, going about their own mysterious business. Dressed in identical tattered robes, there is no way to tell one of them apart from another.
Everything in the Librarium, from the shelf-walls and floors to the staircases and streets, is made from a smooth marble-like stone that has proven utterly indestructible so far. There is no way to so much as scratch the stone, not by diamond, acid or spell.
The unknown architect who designed the city appears to favour domes, air wells, and tall floor-to-ceiling windows for ample natural lighting. Many buildings within the city also feature curved alcoves and reading pedestals, making it seem likely that the city really was intended to be nothing more than a giant library.
A series of windcatchers and qanat tunnels, the latter of which is fed by the lake on an adjacent mountain, ensure that the entire city is kept cool, dry and well-ventilated despite being right next to the Shifting Sands.