Chaeronia is a former Adeptus Mechanicus Forge World that was taken into the Warp for over 1,000 standard years of subjective time, but only 100 Terran years in real-time. It is ruled by the Dark Mechanicus, although there are still a few loyal Adeptus Mechanicus troops present.
It was home to an STC Titan, which was destroyed by the Grey Knights. It is likely that the planet was destroyed by an Exterminatus order by the Inquisition due to the extent of tech-heresy that encompassed the entire world by the time Chaeronia returned to the mortal universe.
- Dark Adeptus (Novel) by Ben Counter