Board Thread:Lore Discussion/@comment-14027812-20131027182513/@comment-13446185-20131029030652

Thu'um is definitely something strange.

"His thu'um was so powerful that he could not verbally swear into the office, and scribes were used to draw up his oaths."

-Five Songs of King Wulfharth

''"The most powerful Tongues cannot speak without causing destruction. They must go gagged, and communicate through a sign language and through scribing runes." ''

-Pocket Guide to the Empire, First Edition: Skyrim

"I am Master Arngeir. I speak for the Greybeards."

-Arngeir

What I have noticed is that the Greybeards other than Arngeir speak entirely in the Dragon Tongue for some reason, and that after Wulfharth's death he was able to speak without any destruction being caused.

''"Then Wulfharth said: "Don't you see where you really are? Don't you know who Shor really is? Don't you know what this war is?" And they looked from the King to the God to the Devils and Orcs, and some knew, really knew, and they are the ones that stayed."''

-Five Songs of King Wulfharth

"That night a storm came and visited Hjalti's camp. It spoke with him in his tent."

-The Arcturian Heresy

Take from this what you want.