Board Thread:General Discussion/@comment-25244530-20130907182212/@comment-79.169.184.21-20140209063008

Quite probably it's the wooden mask, in my opinion. He was known as the Jailor, right? or the Guardian. Maybe he was the Guardian of Bromjunaar Sanctuary before being entrusted the mission to defeat Miraak, and since the fight between the two was a fight supposedly so destructive that it separated the island of Solstheim from mainland Skyrim, it would be no wonder that the mask would be knocked out of his face. Maybe he eventually found the mask again but decided to send it back to Labyrinthian as a sign of an inheritance for someone worthy enough to join the ranks of the Dragon Priests and become the next Guardian of Bromjunaar Sanctuary (or maybe he didn't find it at all, having it being found by a Breton who retrieves it there years later, thus being found there also due to that Breton's thugs turning on him) or simply because the people of Solstheim already had sort of a bad impression on Dragon Priests as rulers (thus refusing the mask and sending it back as he was a just leader for the people according to lore) or both.

At least that's how I see it.