My powers of Threadnomancy are strong!
Just a thought to add to this having read Age of Darkness. In the story where Thousand Son survivors go back to prospero and get ambushed, the one remaining Thousand Son at the end is a Corvidae(with the raven symbol) and towards the end of the story it seems to be focussing heavily on the raven symbol on his shoulder pad.
As someone mentioned before Ahriman mentions that he knew the Blood Ravens first Chapter Master personally, it could be implied from Age of Darkness that this lone survivor could be him.
Just a thought...