Fire Sea: The Death Gate Cycle, Volume 3

Abarrach, the Realm of stone. Here, on a barren world of underground caverns built around a core of molten lava, the lesser races -- humans, elves, and dwarves -- seem to have all died off. Here, too, what may well be the last remnants of the once powerful Sartan still struggle to survive. For Haplo and Alfred -- enemies by heritage, traveling companions by necessity -- Abarrach may reveal more than either dares to discover about the history of Sartan... and the future of all their descendants."