Why did the et'Ada participate in its creation?
Lorkhan told the other spirits that his new world would be cool, basically.
How come the gods have multiple personalities(auriel/akatosh,lorkhan/shor)?
The Gods "died" with the creation of the convention.
Now they are laws of nature and as such, following the inner workings of the Mundus, subject to mythopoetic forces.
They are shaped by the belief of mortals. If the Nords deem the Time Dragon to be a world eater, it becomes a world eater.
If the Imperials deem the Time Dragon a good guy, it's a good guy - but that doesn't mean it's no world eater at the same time.
Two sides of the same thing, two ways to look at Aka.
I want a full explanation of Nirn's creation.
http://www.imperial-library.info/
http://www.uesp.net/wiki/Main_Page
I don't want to be rude, but also: the word "please" wouldn't hurt.