Alright, I have no idea what we should do in this situation, so instead I'm going to offer advice for once we get back to Balmora. This is all stuff that we should tell Caius about the future of the empire, and how he can improve it. He is probably going to disbelieve what we say, or at the very least take it with a grain of salt. All the same, he should be informed of these things at some point. I'm gonna toss it into a spoiler because it might get a little long winded. Also, while writing this, I am going to go with allowing the general main plot of the games to happen, but lessening any death or suffering that would come with it.
Warning: Massive amounts of lore on the Oblivion crisis in this spoiler.
In 3E 433, The emperor will be murdered by a group known as the Mystic Dawn, who will also murder all three of his sons. Soon afterward due to the dragonfires being put out gates to the Deadlands will begin opening up all over Tamriel, spewing forth daedra. One of the most notable locations where A gate will open will be right next to Kvatch. The defense of Kvatch will be utmost, as within there will be Uriels bastard child, Martin. Martin will be a priest of Akatosh in the temple in Kvatch. It is of utmost importance to save Martin, as he is key to the defeat of the Mystic Dawn. The Mystic Dawns main goal will be the summoning of Mehrunes Dagon to Tamriel. While this is all happening here, the city of Ald'ruhn will also be attacked with an invasion of daedra. The Crystal Tower on Summerset Isle will also be the focus point of an major invasion. Now, at some point during all of this, someone will approach Jauffre, with the amulet of kings. This person will be incredibly important to the war against the daedra, as he will essentially be a very powerful force against the daedra, as he is more than capable of entering the daedric gates, and disabling them via the removal of a sigil stone within, which will appear to be a rolling ball of fire. My suggestion is to provide the hero with all the resources of the blades. Fort Sutch will also be struck by an attack from one of these gates. In Bruma, Saveri Faram and Jearl will both be spies for the Mythic Dawn who will be spying on Cloud Ruler Temple. Soon afterward, gates outside of most major towns of Tamriel will open none of these gates will have any real force coming out besides the one outside of Bruma. Soon after this, a massive gate will appear outside of Bruma that will destroy Bruma unless destroyed itself, via the taking of a Great Sigil Stone from within. Around this time, the dragonstone will be taken by the mythic dawn. The Hero I mentioned will retrieve it from a realm of the leader of the Mythic Dawns creation. Martin will then take it to the dragonfires, while Dagon mounts a massive assault on the Imperial City. Dagons avatar will appear, but Martin will be able to transform into an avatar of Akatosh to banish him back to Oblivion.
My suggestions for defeating the enemies would be a much larger detachment than normal be directed to Kvatch early in 433 for defense. Also, as the imperial legion will likely withdraw from Morrowind to better defend Cyrodil, the Empire will earn the ire of most of the dunmer people. I would suggest a massive recruiting campaign starting very soon to help counter this, and all the other effects of the oblivion crisis. I suggest that all knowledge of Martin be kept solely to top government officials and the Blades, as he is integral to the survival of Tamriel. To be honest I would just suggest a massive amount of recruitment. I would also suggest staying away from conscription as that may simply upset the people more than they already would be.
Any additional corrections or info here would be greatly appreciated.
Also, we could simply offer a few names of people that would need to be assassinated for this to never happen, but I'm not entirely sure that wouldn't cause some kind of quantum screw up that would explode the universe or something.Also, I apologize to anyone who is willing to read the above wall of text.
Edit: I would also suggest to Caius that he gets out some paper to write on.
Edit2: So no giving specific names for killing,but still allowing for additional defenses to be put in place may work.
Edit3: So I'm now going to go with referring to the mythic dawn as a cult, as that would decrease the likely-hood of Mankar being taken out before the hero gets rid of him. Possibly not even refer to Dagon as Dagon, merely as a Daedric Lord to reduce the chances of the blades learning about who will perpetrate the crisis beforehand.