I made a thread two days ago about an Emperor whose name I could not remember that Amaund Motierre mentioned. Well after significant amounts of back tracking I have made by way back to The Silence Has Been Broken quest line. Upon interrogating Motierre for information on why he wants Mede II dead, he mentions that Pelagius Septim was assassinated by the Dark Brotherhood. Here is a direct transcript of the relevant information:

Motierre: In the year 3E 41, Emperor Pelagius Septim was murdered in the Temple of the One in the Imperial City. Cut down by a Dark Brotherhood assassin. His killing ushered in, shall we say, a necessary change in Imperial policy.

Now given that we have every indication of Motierre belonging to the Elder Council, and wanting to use Mede's death in order to gain something for himself; the example of Pelagius Septim being assassinated in just the same way as Titus Mede II will be by our character's hands must be relevant. Any reason could have been given but this information is oddly specific given the vagueness of his motives. I can only assume that something happened when Pelagius died that was crucial to the way Tamriel was ruled from that point on. Going off of the change in rulers, I can then only assume that Pelagius' mother Kintyra Septim was the one who wanted him dead in order for her son to take his place. This is typical of interfamily warfare between ruling families, but the big wildcard here is who it is that Motierre planned on having replace Mede. It certainly was not himself, a hit of this size would have taken a literal cabal of conspirators. On top of that we flat out eliminate any major players from Mede's family, potential extended family by way of marriage, and extermination of military Coup d'état. Now the cards lie on the table in a jumble, and the true player has yet to yield their victorious hand.

So gamesas, who is it that you have in the wings? Care to give us a hint?

Here's my theory: Titus Mede II is a mega-genius (at least compared to Uriel Septim) and knew that, what with the Thalmor's propensity for spying and brainwashing, he needed to be absolutely certain of the trustworthiness of his elder council. He had his agents "reveal" to every single member of the Elder Council that they were "secret Septims / Medes" and so could claim the throne (for the Thalmor or themselves) if they assassinated the Emperor. Mortiere was the only one to try and use the DB, and that's why they needed to sacrifice two body doubles in their attempt to kill the traitor.

While I certainly believe that the two body doubles theory has some legs, I am not wholly certain of its validity for a number of reasons. The Emperor, if he was still alive, would probably be expected to actually make it known he was still alive. By this time the most immediate threats would have been eliminated, so there would be no reason to continue faking his death. Then we have to look at Commander Maro and Vittoria Vici. If Maro was aware of this plan; which he should have been, then he mostly certainly would not have attacked the Dark Brotherhood assassin with intent to kill. It makes far more sense for them to try and take you alive and figure out who hired you. With you dead, and the safe house razed they lose their only way of knowing who on the Elder Council is a traitor. As for Vittoria, unless she did something to cause the Emperor to hate her I somehow doubt that letting her die and tossing one of the most powerful resolutions by marriage between Skyrim and Tamrial go wasted.

And why would the second bodydouble be so damn calm? Not trying to fight or anything?

They weren't anticipating the spillover. Maro was pissed because you killed his kid, and acted irrationally. Nobody expected you to kill Vici.

- My purely imagined explanation.

I feel like your post has a lot of Merit, and deserves more replies, but this is really all I have to say.

Well titus II Is a complete badass....