From the back of the book:
Adventures on the Fringe
As the Phoenix Empire encroaches further into barbarian space, its explorers - Questing Knights, missionaries, traders, spies, and dissidents - rediscover worlds that were once part of humanity's spacefaring commonwealth, lost during the Fall. The intervening centuries have greatly changed these systems and their inhabitants. Will reconnecting with them bring prosperity of danger? Some of these worlds' secrets threaten to challenge the power of the Imperial throne and even the souls of Known Worlders.
Lost Worlds describes nine "Lost Worlds" - star systems that were cut off from the Known Worlds after the fall of the Second Republic a millennium ago. Antioch, Eridol, Heaven's Ridge , Kun Lun, Lamorak, Novgorod, Pandora, Sargasso, and Twilight. Also included are: the nizdharim, the tentacled sentient mollusks of Hargard; the Z'go, sentient energy beings; the mutant Qabirim super-intellects; and many alien creatures encountered in barbarian space. Finally, there's the Emberhawk, a fast freighter popular among fringe-world merchants complete with deckplans.