Restored World Nviro-IV, Auriga sector, was once covered in a world-wide city environment; almost all trace of this civilisation has apparently been removed.
Like the Dawn Hunters, the Restorers are part of the folklore of the Terragen Bubble. No original Restorer nanites have ever been found (or even any microfossil traces), and no-one knows if Restorers exist, if they are the same as, or employed or created by the Dawn Hunters (if they exist), or if they are just one more galactic myth.
The Restorer Hypothesis was first suggested in a seminal but controversial virchpaper by Academician Ralen Vuyrygi of the Eden Institute of Xenology, in 3285. Returning from a relativistic mission to Serentis-3, Acad. Vuyrygi noticed that almost all traces of the original Iahi Daon colony there had been removed, leaving only a few deep structures that were only visible from orbit, and even then only by careful gravitational measurements of the planet's crust. A similar phenomenon had early been found in the southern continent of Nemo, but this was dismissed until Acad. Vuyrygi presented eir thesis. In his paper Acad. Vuyrygi speculated that degradable nanites of an unknown origin and design had been purposely seeded by an unknown xenosophont species, and removed traces of civilization from Serentis-3, and that these same nanites had been employed but had failed (possibly due to local climatic, chemical or biological factors) on Nemo. In the virchpapers oft-quoted and copied concluding module he suggested that further worlds should be re-examined for traces of civilization, and confidently predicted that these would in fact be found.
In the millennia since, many such deep structures, geological anomalies (evidence of mining and manufacturing), inconsistent isotope ratios, and (on garden worlds and others inhabited by lifeforms) palaeontological evidence of local ecosystem disruption, all indicative of extraterrestrial colonization, have been found on a large number of worlds throughout known space.
Yet at the same time, other worlds have been found - sometimes - as in Landios (YTS 2104-5613-5) in the very same solar system, in which there has been no alteration or attempt at cover up. And there are whole swathes, as in regions such as the Inner Perseus Arm (Metasoft Territories) and along the Serpens Volume - where alien ruins are to be found in their complete state. The Vuyrygi Thesis fails to explain how these supposed "Restorers" could be so random or inconsistent in their efforts.
Academician Ralen Vuyrygi, 3285, "On the artificial origin and nature of deep structures in the upper lithosphere of Serentis-3, and a possible resolution of the Fermi Paradox." Xenology VirchPapers, no. 271098, Eden Institute of Xenology
Milon Chandigo, 6921, "The Vuyrygi Thesis, and the problem of non-erased paleoxenoc ruins." Journal of Xenology, vol,5,231 part.3 , Eden Institute of Xenology
Yun Riol-3128 , 10142 "Dawn Hunters, Restorers, and other things that go bump in deep space", in Myths to live by: Galactic Folklore amongsophonts of sub-hyperturing grade, Corona Galaxy Books, Corona