So as I was playing Dragonborn and exploring all the new Black Book perks something dawned on me. After using the upgraded unrelenting force shout and disintergrating some bandit I remembered all the controversy of when the high king of skyrim was killed, he was blasted apart by Ulfrics shout. Now if the dragonborn cant already distintergrate people with their voice without the help of a daedra then it stands to reason that Ulfric certainly couldn't on his own. Unrelenting force is so far the only shout that disintergrates (aside from the effects of soul tear), and Stormcloak has been shown in game using it. Which means that at some point he must have happened upon the black book "Epistolary Acumen," been transported to oblivion, been in contact with HM, and worked out a deal to get the perk that upgrades fus ro dah. Perhaps the civil war was one of HM's plots and Stormcloak was just another pawn, and by supporting the rebels you're indirectly helping a daedric prince. An new perspectice brought on the civil war thanks to the dlc

The High King being blasted apart was hyped up rumor. Ulfric will tell you himself his thu'um knocked Torryg to the ground and his blade to the heart ended the High King's life.

Ulfric killed the the high king with his sword.

this, in game ulfric can't shout people to ash either, just propaganda both sides use

I was disappointed that I couldn't pledge my allegiance to HM.

He is my master now and I do his bidding.