The Athan were a race that existed thousands of years ago.
They invaded the planet Zchol and conquered its original inhabitants. The Athan also held Orions in slavery by the Treaty of Kammzdast, so they imported a small number to serve them. The Athan came to consider Zchol their new ancestral home.
The Athan of Zchol were in turn invaded and conquered by the Shani. The Orions remained to serve the Shani. Some Athan remained on Zchol, but were decimated and eventually fled during the Reverse. (FASA RPG module: The Orions: Book of Common Knowledge)