Board Thread:Lore Discussion/@comment-209.7.3.188-20160303204000/@comment-26893431-20160511203659

Ashley Kirshbaum wrote: Nafalilargus was killed by cyrus. he may or may not have been resurrected by alduin, but even if he was, he wouldn't have had enough time to teach the ebony warrior, as alduin has only just returned and it takes a non-dragonborn years to learn a shout. there have to be other people around who know the thuum.

the imperials would likely have framed Ulfric with foul murder regardless of whether the duel was fair or whether he announced his intentions beforehand, as they cannot allow an independent skyrim to happen. it would weaken the empire too much, and thus make things easier for the dominion.

i don't see how usage of the thuum is unfair. it is a skill that takes a lot of effort to learn, so mastery of it shows that the person has great willpower. Even then, there's still Nahfahlaar. A dragon can pass on his understanding of the word, (like the Greybeards did with for example Fus Roh Dah).

That's speculation.

Because the Thu'um is only accesible for a select few who get chosen.