I am the Chosen One! Specifically, the "Moon Hallowed," whose job is to guide the prospective new Mane in the process of becoming the Mane. I think. Anyway, this is actually the first time in the game that you're explicitly made a chosen one of any kind. It's funny, because I remember in the advertising and promotion of this game, they kept talking about how in the main story, you were the "Soulless One," a hero predestined by some prophecy to defeat Molag Bal. That all turned out to be crap. Dumbledore gives a few generic "There's something special about you" comments at the start of the game, but there's no prophecy, no talk about fate or destiny, and the PC is referred to as "the Vestige" throughout, which is, needless to say, a far better name than the Soulless One. It's like the dumb "derp transcription error" tweet I linked earlier - I think there was some real miscommunication between the developers and whoever was promoting the game.
No, I will not shut up. I'll keep talking about the main story, particularly because I want to correct an old post of mine here:
I'm a little confused about how the main story is going to work. I had thought that the war was just a PvP thing that would always be going on throughout the course of the game, but now it's being tied into the story? You have to win the war and become the emperor so that you can fight off Molag Bal for good? But then what happens with the PvP area and the Dark Anchors - are they just not there anymore? 
The Kotaku article in the post from Snupes that I was replying to doesn't seem to exist anymore, but I summarized what the author said about the story, and she was way off base. You don't become the emperor or win the war. You do mount an invasion of Coldharbour after you've completed your faction's storyline, but it's basically a coalition of people from the Fighters and Mages Guilds. The three faction leaders outright refuse to participate, for fear that it'll weaken their own war efforts. Anyway, the main story itself, with the Prophet and all, is more about trying to find a long-term, so to speak, solution to the chaos, by trying to find the Amulet of Kings. But at the same time, Mannimarco is looking for the Amulet, because his plan is to use it to usurp Molag Bal and become a god himself. Somehow. He's not exactly clear on that front.
That aside, Mannimarco is pretty cool. I honestly think that he was included as an apology for how badly Oblivion bungled him. (I would seriously welcome a retcon of his death in a later TES game. They could say that it was just some body double you killed while the real Mannimarco made his escape. Given how easy he was to take down, who could argue with that?) The only issue I have with his portrayal is the fact that, as I mentioned earlier in the thread, he seems to pretty unambiguously die. Molag Bal drags his soul into Coldharbour for some torturing, too. In a later quest, you meet him while he's being punished, have the option of freeing him (I have no idea why) and he says something about being neither alive nor dead. Uh huh. And bear in mind that this is the young Mannimarco, centuries before the Warp in the West may have given him any divine powers. He wasn't even a lich at this point. This is the biggest question mark I've encountered in terms of lore, but that's probably to the game's credit, all things considered.