User blog comment:Timeoin/Jorunn the Skald King/@comment-1992639-20121206132955

"For reasons that have not been divulged, the Greybeards summoned a hero from Sovngarde, Wulfharth the Ash-King, to fight at Jorunn's side."

This makes me curious about the Akaviri having more than one motivation to attack Skyrim. Were they perhaps after Paarthurnax? The Greybeards wouldn't stand for it and would probably act, which they did.