Mehrunes Godsbody, not Akatosh, shored Oblivion. Dagon gave up his Protonymic to the Dragon Fire, the Iniquities' occult "loophole," whereby heaven's kind defile Nir. ...

The villain Calaxes conspired with the incorporeal sorcerer for an opportune time, when their doppelgangers... and one betrayed the other. Tharn withdrew into Aka's Diamond.

Deluded to believe he held the mastery, the sorcerer didn't realize another door had been forged within Cloudruler's Temple - Calaxes had him trapped (never deal with the Dragon). If Tharn had predicted Calaxes' initiative...

... The traitor-priest only impaled his Hunger on the Protonymic. And I think, in honor of [Sanguine]*, I'll close with living proof: http://www.imperial-library.info/content/fight-one-eating-birth-dagon

(This is the part where you fall down and thank Dagon for saving the world. Again.)

*Poetic Justice