Doesn't that happen anyway?Atleast,thats the impression I got when I killed the tribunal,Mannimarco and other liches.

In theory, while the Tribunal were regularly connected to the Heart killing them would have worked more like it did when you killed Dagoth Ur the first time, and he just reappeared in the next room (actually, the way knocking people unconscious works in Oblivion is probably a good comparison as well, just substitute regaining consciousness with coming back to life).

Vivec had this to say on the subject of his immortality (and subsequently, dying):

I think that Caius Cosades is a good fit for possibly being the hero from Daggerfall, as he had the least fame and fortune after his service, it just seems to fit for me

Interesting theory. Doesn't Caius also have a copy of 'The Warp in the West' laying around, too?

Book's in the wrong game.

Under his bed I think

I'd also like an account of what it looked like to the outsider when he died, what the second party experienced if they 'killed' him. Would they even notice that he had died and came back. Would he reappear in the next room, or in the same room, in a 'new body' like Ur. Would it look like he got knocked out and regain consciousness.

What does it look like to kill somebody who automatically returns upon death, or does it even look like anything, unnoticeable... Perhaps it's like asking what it looks like for the npc that kills the player character, assuming the player character had just saved before death.

I think it would be like Gandalf in LOTR, he becomes ineffective for a time and then comes back

Considering that book didn't appear in the series until Oblivion, I don't think so. However, on that note, I would like to propose a theory of Jauffre being the Eternal Champion based on his age, high ranking within the faction of the Blades, his personal mention of Jagar Tharn, and his long history with Uriel Septim VII as revealed by the details of Martin's birth.

I have considered this possibility alsol, being a Breton and slightly longer lived he is at a reasonable age, give what his age would be, it is understandable that he would want to retire, (and his position indicates he has done some sort of service to the Septims),

Considering that Uriel Septim even seemed to trust him more than anyone when Martin was still an infant also seems to indicate that he did something remarkable to obtain such trust at what would had likely been a relatively young age.

One hole in this theory is that you would think he would have a bit more knowledge about Oblivion, having rescued the emporer and all, it is also unclear whether Martin was born before or after Arena, (as Uriel looks pretty old in Arena and Martin has had quite a few experiences, placing him at about 25-30 years old?, not sure how long it is between Arena and Oblivion it's about 25 years though so maybe it is a sound theory)

Arena ended about 34 years before Oblivion began, if I'm remembering things correctly. I just checked and the UESP confirms it. Arena ended in 399 while Oblivion began in 433. Uriel Septim was locked up for 10 years in Oblivion and I doubt Martin is at least 44 years old. Jauffre also said that Uriel would ask about the boy's progress from time to time, and Uriel can't do that from Oblivion. It may have been Tharn who did it, instead, but I don't see how Tharn would know about that secret nor why he would care about the boy's progress. Tharn would have likely just killed Martin if he knew of his existence. If Uriel asked about the boy's progress from time to time, then he must have truly been a boy progressing and for that to happen, Martin must be at least about 50 years old or he must have been born after Arena. I believe the latter is more likely. At Arena's end, Uriel would have been 53 years old, and so I believe he may have had a child, at that point. Men never stop producing sperm, in our world, and men as old as 90 have had children, in our world.

Okay, I suppose it is rather likely that Uriel would still e able to get women in his old age, being a rich emporer with Patrick Stewarts voice and all

This Jauffre theory also explains why the eternal champion wasn't around, because he was, Jauffre also identifies with the CoC, as neither of them saved the world for themselves,(CoC, was behind the scenes while Martin was the hero and the Eternal Champion was also bound by service to the emporer, rather than being a proactive hero himself, the EC is reactive in Arena, he isn't trying to change the world, only to restore it) Jauffre also seems uite humble about his achievements, explainin why he doesn't announce himself as the EC

EDIT: Martin may be older though, as to become an acclomplished, Daedric follower, Priest and mage he had to hve gotten around, and Tharn may have usd his magely powers to influence Martin to the deadric path, perhaps grooming him to be a succesor

Or perhaps he planned to use Martin to banish Dagon by doing what he did at the end of Oblivion, Tharn ws a devious bastard, and would have probably wanted a way to eliminate Dagon if he was planning not to honor an agreement

Of course, we have no clue if Bethesda was intentionally implying any of this or not, but I find it hard to believe that the savior of the Empire would just disappear, as lore states. I believe Uriel would have given the Eternal Champion a high-ranking job that involved continuing to protect him and, while this is a crackpot theory of its own that obviously is not considered canon, I like to pretend it's real. I think that's an excellent anology. Just like the EC, the CoC will likely also fade into obscurity, as well. Mortals wouldn't know about his mantling of the Madgod.

True, there should be a reference in Skyrim to the Shivering Isles MQ, like a quest for Sheogaroth, and him making comments on once being mortal or something

I'd like to think that Tharn was in Mankar's position, though, which is to say he was in control of what was going on and was using Dagon as a tool. However, I know I can say one thing about Martin in relation to his father. If he truly was about 50 when we knew him in Oblivion, he looked nothing like his father when his father was the same age.

He would have been a bit healthier, being a farmer and all not a cushy emporer Tharn always seemed a bit more intelligent than Mankar, and more out for himself

In one of my wilder and crazier theories, Tharn used his decade in power to engineer essentially the next 250 years or so by maneuvering the proper people into the proper places and most of all that Mankar was just a pawn to catalyze the entire process. He even used Mehrunes Dagon... for whatever reason and knew that someone would stop him from invading via the Battlespire. My problem of course is the question: to what end? and to that, I don't know.

I'm hoping that Tharn makes a comeback, I personally think he (as Uriel) engineered Martins life so that he would do what he did, perhaps to unleash Akatosh on Tamriel? I doubt he would have left his life jewel just laying around, he could have faked his own death, all to eliminate Dagon

Mankar was supposed to be Tharn. The Mythic Dawn was supposed to be Tharnatos. That story-arch is, unfortunately, gone.

I wouldn't expel mythic dawn from my Tamriel, though. Their yogins go about, most K'vatch, choreographing the dances of the Magn Ge. The dance is perfect, a moth takes their soul up, and they take a star. Something likr that. Tharnatos are the assassin/revolution Dagon cult.