[Zigûr]

Originally Posted by Dark Lord

Secondly, I must point out, before I ask my question, that Sauron, is my absolute favourite character ever to be created.

Understandable! Sauron is one of my favourite characters invented by Professor Tolkien (which may be obvious from my user name and avatar) but personally I find him fascinating rather than liking anything about him as such, or feeling sorry for him. However, I think his characterisation in The Silmarillion etc is incredibly interesting. Apologies therefore for the long post - I could talk about Sauron all day.

Originally Posted by Dark Lord

Couldn't Eru resurrect him, or give him some power?

Given that he was in the habit of claiming that Eru didn't exist and that Morgoth (earlier) or he himself (later) was the real God despite having personal experience of Eru's existence, and that this was considered to be "an abomination" (Letters p.243) I somehow doubt that Eru would be very sympathetic.

Originally Posted by Dark Lord

I heard that The Blue Wizards were some sort of necromancers and that someone said that they could bring Sauron back. True?

I think this might be a case of misinformation. Professor Tolkien once speculated that the Blue Wizards could have been responsible for the establishment of harmful cults in the East (but also that they might have actually helped a good deal in promoting resistance to Sauron among the Easterlings). They are not, as far as I'm aware, ever associated with Necromancy. Regardless, "Necromancy" in Middle-earth is largely about manipulating spirits (particularly of dead Elves who refuse the call to the Halls of Waiting) rather than the modern interpretation of "bringing people back to life", which is pretty much impossible - Elves could be reincarnated in Aman and Ainur could rebuild their own bodies through effort of will but that's about it, and it was too late for Sauron to do that (see below).

Originally Posted by Dark Lord

What about the last battle? Dagor Dagorath. I read that Melkor, will break open the Doors of Night and him and Sauron shall escape the Void, destroy the moon and the sun, and that all evil things will fight with the free people's and that Sauron will be in it as well.

Does anyone know if Sauron will dies during the battle? Does he even have a physical form then?

Would he have his power back or will be be extremely weak?

This remark from the Professor in Morgoth's Ring seems relevant:
"Melkor was not Sauron. We speak of him being 'weakened, shrunken, reduced'; but this is in comparison with the great Valar. He had been a being of immense potency and life. ... The dark spirit of Melkor's 'remainder' might be expected, therefore, eventually and after long ages to increase again, even (as some held) to draw back into itself some of its formerly dissipated power. It would do this (even if Sauron could not) because of its relative greatness." (p. 404)

Evidently it was not within the capacity of Sauron, a comparatively lesser being, to restore his lost power.

Originally Posted by Dark Lord

Would they destroy him forever? So he has no spirit form or physical form, so he is basically dead? Please not let this be true, he deserved to rule ME in my opinion.

Given that Sauron was, in the Professor's words, "as near an approach to the wholly evil will as is possible" (Letters p.243) it would suggest to me that in the final analysis he would be either destroyed or left totally impotent forever. As far as deserving to rule Middle-earth, well... at least as far as the story itself goes, Manwë was High King of Arda by divine right so that kind of precludes any other ruler from being morally acceptable on such a scale (as far as the internal logic of the story goes).
As interesting as I think Sauron is, he's still a murderer, liar, warmonger and tyrant superseded only by Morgoth himself!
At the end of the First Age there might have been some hope for his recovery, but by the end of the Third I think it's fair to say that the story considers him to be beyond redemption.