Join Date: Aug 2009
Location: Portland, Oregon
In Prospero Burns, the daemon in Horus's guise says, "Two key obstacles to my ambitions are the Sons of Prospero and the Wolves of Fenris. The former is the only Legion that has lorecraft enough to hinder me magically; the latter is the only Legion dangerous enough to represent a genuine military threat."
It's easy to see the Thousand Sons having the lore or knowledge to hinder the rebellion--perhaps by clearing the Ruinstorm or banishing the very important daemonic allies Horus will use on Terra. The Space Wolves is a trickier question.
It states the only Legion to pose a genuine military threat...
I don't know. Maybe the Wolves were destined to be on the fields of Istvaan V, but instead of being shocked by the betrayal of their brothers, the Wolves would have rallied the Salamanders, Iron Hands, and Raven Guard and blasted their way through the Traitors and made good their escape?
But this is before Istvaan III, much less Istvaan V (which wasn't originally planned by Horus...his hand was forced when the Eisenstein escaped).
Then again the Warp doesn't give a poop about linear time, so who knows?