Hell is a location linked to the Library; whether the two share the same plane of existence or if they are two separate but linked pocket dimensions is both debatable and most likely irrelevant. For Hell shares the Library's flagrant disregard for the norms of Creation, albeit taken to a far more extreme conclusion. In Hell, mortals are able to conjure up whatever they wish through sheer willpower. This phenomenon is attributed to a structure known as the Shuddering Spire.
Mortals find Hell in a fashion similar to finding the Library; through a dreamlike state in which they are given the option to proceed towards Hell or turn back to Creation. This usually manifests as the traveler either walking down a foggy path, or drifting down a dark river, guided to Hell by dim lights. There are less cryptic pathways leading from the Library to Hell as well.
The entirety of Hell is "governed" by the Republic of Hell, and the Impostor Church dominates local "politics".