If akatosh saves the world from the oblivion threat in TES:4, why would he come back to eat it in TES:5.Did he banish dagon back to oblivion just because he was a minor inconvenience to his major goal of eating the world any ways.

It's very likely that when Martin smashed the amulet, the covenant between men and Akatosh broke, and now Akatosh is now free to roam of Alduin. The altmer of Summerset are likely to favor this, as they view Mundus as a prison, Aruiel (mer akatosh) as their savior and protect and thus against Mundus, and if Akatosh can devour this kalpa, the "prison" will be destroyed.

Perhaps what the dagonites did in OB was an unplanned plan B, as Dagon is the cursed kind leaper demon king, who taught many to cut corners and jump away from Alduin's mouth. With the removal of Mundus, Dagon could go back to being the leaper demon king again.

Anuiel isn't Alduin, although they may share the same goal. And the Covenant can't be broken, because there had to be some sort of deal for White-Gold to stand again and the invasion to be halted.

There's not a unified will behind every incarnation of the Dragon, neither is he sane. He is more than capable of fighting amongst himself.

Little known secret, the White-Gold towers stood long before any Man came into play.

Well, Chim-el Adabal is an Ayleid Stone.

There's nothing to suggest this at all. Quite the contrary, in fact.

The Dragon God of Time is destroying the world because he's the god of time and, in Tamriel, time comes to an end.

You do realise there is a thread like this less than half a page down?

Damned you got to it before me.
*eats the world*

Bleh, I got the name mixed up, whateva.
Well, I see that the god of goody goody time pretty much gave his last bravado, then went back to his all consuming self.