The campaign is based around the Crag Mountain Fastness, a major dwarf mine in the North Mountains.
The campaign is sequenced around the discovery by a maintenance team (the PCs) of a hidden underworld and prison, once the domain of an ancient race of advanced dwarves. They “delved too deep” and awoke terrors – spirit-demons ( hoodwraiths)
The opening of the hidden world finds they have been let loose once more for, thousands of years ago, they were captured and sealed within prison-globes by an alliance of intelligent races, now called the “ Ancient Alliance”. Many of the globes were smashed by an unexpected earth-movement (the Crag Mountain lords believe the machinations of an evil being as the location should have been stable).
The prison, though, was arranged around a pair of magical world-maps arranged around a portal: the world-maps give the locations of every wraith in the world and the other planes as well as the location of numerous portals (and their addresses). Using normal portal magic, a group can travel close to almost any wraith troublespot they can see on the worldmap.