From the back cover:
The ancient and fragile map found in the party's latest treasure tells of a pocket dimension, of the blasted and barren planetoid within, and of the spectacular mausoleum upon the forbidding rock. The treasure was hard won and the map obviously kept with some care, but could such be true? What type of creature would build a tomb complex so far from the very eyes such things are typically meant to impress?
Regardless the how and why of the place, the forsaken sepulcher lies out there beyond the realms of normal adventurers, waiting for brave or foolhardy explorers to step through a special gate and view it in the flesh.