From the publishers website:
Terrors of the Dead Lands presents the undead of Athas, in Dungeons and Dragons 3rd edition format. Old terrors are back, as well as new undead, and other creatures for the Dark Sun world. Many of the new undead are an important part of the upcoming Secrets of the Dead Lands accessory. You'll find rules for creating new undead, templates for powerful new forms of undeaed, and even a few living terrors.