Guys first post in awhile, so hello!
So, while I am really strong on the World-that-Was lore, I am admittedly weak on AoS lore. Anyhow is there any suggestions in the current narrative and/or supplement materials on who the "mighty ally" that Nagash is trying to free from the Stromvaults mentioned in that text extract might be? Any thoughts on whether it is some from his former Mortarchs for which we still don't have models for or something completely else? Also, does it tie up with the couple of rumor engine teases with deathly aesthetics in any way?