User blog comment:KarebCree/Thorian -- a possible 'first' Reaper race?/@comment-4491632-20120602202246/@comment-5124423-20120602205737

Yeah, and it also explains why the Thorian was so special. It had just a single performance in the entire series -- unlike all other enemies. But it has this certain link to the Reapers, similar abilities and traits. That is why -- probably -- it didn't need to have a bigger role.