Prophet Seed

It is the year 8729. Man has spread himself throughout much of the cosmos; conquered innumerable new star-systems and converted their worlds to his exploitation. In the doing of it, however, there has been war; a war that is only now coming to an end after raging for a thousand years. On Avalon, a pristine, Earth-like planet that was once a mining concern, the old colonists that were abandoned there at the onset of the war, have changed. Having been cut off from the empire of man for a thousand years, they have all but forgotten their original roots and purpose. They've gone back to the land; back to an iron-age, near-barbaric existence, and they now harbor a dark secret among them; the fantastic results of sins that were committed long ago.
This secret holds the power to forever alter humankind as a species.