During the Galactic Empire's reign, it was rumored that the Imperial Navy possessed an Asteroid Dreadnought, a dreadnought disguised as a space rock. Rebel Alliance Intelligence Service Colonel Haxen Delto penned a report for Chief of Rebel Intelligence General Airen Cracken concerning Imperial superweapon initiatives sometime between 14 and 19 AFE; the report contained a segment addressing the dreadnought rumors.
Within the report, Delto conveyed that he wouldn't disregard the rumors of the starship, even though he acknowledged the unreliability of the Rebel Alliance's informant within Patriim. This report was found in The Rebel Files, a collection of sensitive data preserved in non-electronic format, which was uncovered on the Mid Rim world of Durkteel decades later.
The Star Wars: The Rebel Files boxed set and reference book, written by Daniel Wallace and launched in 2017, was the first place the Asteroid Dreadnought was mentioned.