The Catacombs are a section of the Radivan universe. It consists of 14 polities, several hundred wormholes, and a huge number of empty or nearly so systems. The Catacombs are notable for huge numbers of well connected wormholes in deep, empty space. There are hundreds of routes between polities, most of which don't pass through any other state.
In most of the wormhole system, there is only one or two routes between two near-neighbors. If they're not one hop apart, it's usually necessary to travel through anothr state. This makes interstellar traffic in most of the galaxy reasonably traceable, and makes piracy very rare. The maze-like nature of the catacombs means its possible for pirate ship, or a ship that has been hijacked, to disappear. The maze-like wormhole map, prevelance of piracy in a former age, and the numbers of dead ships still drifting from those days are what give the sector its name.
The polities of the catacombs are seperated into two groups. The Junction attached and the Binf attached. From any of the polities in the Junction attached group, it is possible to reach any other, without crossing into a third. The same applies to the Binf attached group. To get from the Junction attached group into the Binf group, or vice versa, it is necessary to transit through Nexa.