Through the Breach
While the greater Malifaux proper sprawls and covers a massive area above ground, many explorers believe the sewers, catacombs, and dungeons make up the primary stuctures of the discovered city. This vast, unmappable network of corridors and mausoleums is collectively often called simply “the Sewers” or “the Undercity.”
It cannot be stressed enough that the same chaotic architecture observed above can be found below. The Guild does its best to control these potential security risks to their populated portions of the city, but with little to no avail. Arcanist criminals, secretive Resurrectionists, or even the stray Neverborn skinwalker often use these dangerous passageways to avoid overland travel to traverse the City.
Image taken from Guild Wars 2 concept art at http://gw2.gameguyz.com/.