Faces of the Dead Lands

From the introduction:

South of the haunted city of Kalidnay, across a vast expanse of desert, scrub and little else, beyond the cliffs over what seems to be the edge of the world, is a land wrapped in black glass. No image I can put in your mind can do justice to the sheer vastness and emptiness of the Obsidian Plains. Millennia ago, black glass flowed and coalesced over the ruins of every battlefield, every city, and the residents themselves. There are no hidden springs for water finders to uncover, there are no secret oases for you to discover, there are no animal herds to provide hunting, and there are no plants at all.