My candidates...

The Greedy Man. This Skaal legendary evil character was somehow linked to the one they called "Thartaag the World-Devourer". Moreover, greediness could refer to his thirst for Dragon souls and power.

Jhunal. This antic and forgotten Nord God was related to knowledge, and said to have invented mathematics and language. While mathematics belong to Herma-Mora's Realm, "having invented language" might be a deformed account of his instinctive ability to understand one particular language, namely the Dragon tongue. Which is one of the characteristic feature of a Dovahkin.

Yglar. Ysgramor's second son. The http://www.uesp.net/wiki/Lore:Songs_of_the_Return,_Vol_2 tell us that "Ylgar, the younger, was possessed of an unwavering spirit that drove his singular prowess to overwhelming feats in war." Maybe it refers to Thu'um? Since Ysgramor was often an opponent of Herma-Mora, it would be a delightful vengeance from Herma-Mora to turn his last son into an ally.

The Snow Prince. Cause this guy once ruled Solstheim.

Shalidor. His creation of Winterhold by "a breath" might be a clue he mastered the Thu'um.

Divayth Fyr. Because this guy is [censored]ing awesome!

Dagooth Ur. Maybe it would explain why he wore a mask, why Septius Signus thought that the lockbox contained the heart of a God, and why there seem to be ascended sleepers in Apocrypha.

Aevar Stone-Singer.

Miraak. Some guy we don't know anything about. Maybe an ancient Atmoran king?

Morihaus. That guy wasn't named the Breath-of-Kyne for no reason.

Pelinal.

The builder of the Skyforge

Shor.

So, who do you think is the First Dovahkiin ?

My favourite candidates are the first three.

Might want to add the other dragon priest who's mask was wooden, Konahrik. There was a theory proposed by someone in another thread that because we never actually find this priest and defeat him, he's still out there somewhere. Could be on Solstheim. How his mask got into the hands of a traveler is another question.

I like this theory a lot too.

Me too. Jhunal makes some sense to me, as does Shalidor. Shalidor for the sole purpose that he could basically do anything, and Jhunal because I would like to learn more about a God and how he fell from power.

this is a strong possibility.

Nerevarine was a Dragonborn too wasn't he? Food for thought

Or maybe Wulfarth / Ysmir?

Or even Alandro Sul?

What? No. He was a Nerevarine.

The trailer tells us that he is a Dragonpriest though. To me, this implies that he was around during the Dragon Wars, which was a long, long, long time before Nerevarine. Plus we never really devoured any dragon souls in Morrowind. Doesn't make sense to me.

As I stated in the other thread,

According to the trailer, "HE" was once one of the Dragon Priests, and showed the alter of the 8 Dragon Priests where the masks go. In Skyrim, there is a quest that if you collect all 8 masks, you get a 9th one from the dragons mouth. This is "HE" the 9th one. Not the wodden mask, but the last, 9th Dragon Priest. HE is also said to be the first Dragonborn plus he is a Dragon Priest. Dangerous combination.

In Skyrim you have to kill 8 dragon priests to get the 8 masks. Once placed on the proper alter figure, you get a 9th mask. The 9th mask belongs to a dragon priest, but you do not really know the name of the dragon priest, only the name of the mask, plus the 9th mask is the only mask you get without having to kill a dragon priest to get it. So is the wodden mask that is found by the body, that takes you back in time to place the masks on the alter. So in theory, there were 9 dragon priests, and you killed 8 of them and each one turned to ash when you killed them. Where is the 9th one??

The trailer shows a column/stone with people working around it. The same one that blows up. This is the tomb that holds the Dragon Priest that wants to come back like the dragons themselves. It also shows at the end of the trailer, that HE, the Dragon Priest is absorbing not one, but 3 dragon souls, and has no weapon in sight.

Again I ask. Where is the 9th one??

Some veeeerry good candidates, OP! The "leak" in the speculation threads said the guy is called Miraak anyway. But who says he couldn't be The Greedy Man? Or The Snow Prince? "He - - ruled over Solstheim." Hmmmh....

I'm currently torn between these two options, and Konahrik. Two or more of these can even be the same person for all I know, though.

How about Konahrik = Miraak = Greedy Man and/or The Snow Prince?

The trailer outright states that he "ruled in the name of the dragons" It's a sure bet that he was part of the Dragon Cult, although whether he was present for the Dragon Wars is debatable.

It is the 9th Dragon Priest. My theory anyways. It is the only Dragon Priest you do not kill. The only Dragon Priest that did not turn to ash. Konahrik I believe his name was. It makes sense.

But Konahrik has his own mask which was lost in time (and can be found in Labyrinth). It will be awkward to just show up in front of the supposedly long lost Konahrik with Konahrik's Mask and be like "Hey I found your mask... So how's the weather?"

Could it be YOURSELF behind that mask? It would make an interesting confrontation like where you fight yourself in Oblivion. Or it might be just an entirely new character.

ME. I will also be the last. Mwahahaha!

...I..I'm not a very good dragonborn...I accidently used Dragonrend while looking at a mirror...

That is true, and it looks like the first dragonborn has his own special mask from the trailers. I would like some clarification about Konahrik though and why/how he was separated from his golden mask.

Yes, the mask was lost in time, but it is also the 9th mask you recieve after you defeat the other 8 Dragon Priests. It is the only mask where you do not have to fight a Dragon Priest. Dragon Priests were once mortal men and because they were high ranking, recieved the masks. They also betrayed the dragons, and became like they are now. It is also said that a Dragon Priest can easily kill you, no matter what level, unless you are carefull which is why fighting a Dragon Priest is harder than fighting a dragon. The picture at the end could either be the 9th Dragon Priest when he was mortal, or what yourself looks like after defeating him. No telling there, but I believe it is the 9th Dragon Priest. That is what the trailer says, and even shows the Dragon Priest alter.

My money is on someone new.

I'm wondering why you have to fight the guy. Consider:
1. He's a dragon priest and a master of the Thuum, but clearly no friend of dragons. Far from it.
2. His rule of Solstheim sounds like it was pretty benign. How can he be an evil guy?
3. Wasn't Tiber Septim also Dragonborn? Could this guy be someone who could take over rule of the Empire and revive the fortunes of Men against the Thalmor?

Oh, and more on Konahrik:

http://www.uesp.net/wiki/Skyrim:Konahrik

My guess is Talos Stormcrown, but that's probably never going to happen, since the man's long since dead, and one of the nine divines.

EDIT: Ysmir = Talos = Tiber Septim

The description for Konahrik's mask said: "Chances to summon a dragon priest to aid you when you health is low". I think this summoned Dragon Priest is THE phantom Konahrik.

But more and more I suspect that this Dragonborn is not someone new, because other wise they wouldn't give him a mask.

Konahrik was likely the Dragon Priest that ruled over Hjaalmarch. Bromjunaar seems to have held great importance for the Dragon Cult, it might have even been their 'capital' of sorts.

There were 9 masks (not counting the Wooden) in Skyrim and there are 9 holds. The Dragon Priest-born (Miraak) in the DLC governed Solstheim.

I'm starting to like this idea. It would be a pretty awesome twist if he wasn't a character bent on revenge against man/mer and just wanted to help instead after being trapped in Apocrypha for ages. But I have a feeling he's going to be bad and we will duke it out in an amazing voice match that will result in the sinking of Solstheim itself!

I don't think the lore limits the Dragon Priests in number. While we only find nine masks in game, there were likely far more priests.