From publisher blurb:
In the middle of the desert, there is a ring of mountains covered in a cloud of dust. Some claim that inside that dust is a paradise, a relic of the time before the desert, when a mighty empire ruled these lands. A place where the deprivation of desert life does not touch, and riches abound like grains of sand. Others say that only death awaits in the cloud of dust, and that none who enter ever returns.
Exterris can be used as a remote locale in any campaign world, or played in the default setting. It can also be used as the central location in the second installment of Hellebarde's Castles and Crusades Sevich Desert Campaign. This portion of the campaign - The Exterris Adventure Tome - consists of AT-5 plus ONA-17 through ONA-20.