Didn't the narrator in the trailer just say that "he(1stDB) Seeks to return"? Couldnt that mean hes trying to return? As in hes trapped. As in HM is keeping him there? MAYBE we have to save him because only he can help us stop HM from doing somthing bad!

Or stoping HM from doing something good.

He's not on our side. I do believe that he is somewhere else, though. Not sure where in Apocrypha he could be. You go through it before you finish the main quest.

nah he has been made to look to bad to be good, beth went out of there way to make him look bad in the trailer, so yer like they protrayed him as a back stabber a power hungary dictator i don't think he is good

This is a quote from the http://www.elderscrolls.com/skyrim/add-ons/

Dragonborn
With this official add-on for The Elder Scrolls V: Skyrim?, journey off the coast of Morrowind, to the island of Solstheim. Encounter new towns, dungeons, and quests, as you traverse the ash wastes and glacial valleys of this new land. Become more powerful with shouts that bend the will of your enemies and even tame dragons. Your fate, and the fate of Solstheim, hangs in the balance as you face off against your deadliest adversary – the first Dragonborn.

- you start the game with his followers attacking you for being a fraud. He's probably a dike, we just don't know why.

Could be all a ruse. Needed something to get you into Apocrypha... Probably needs your soul to leave Apocrypha.

Kind of like Ulysses from FO:NV? I wonder that myself.