The stories vary but most agree that there were things before him. He was the first to find a way to last or the first that lasted. You could say that he found immortality. Hence he embodies everlasting legitimacy and endurance.
http://www.imperial-library.info/mwbooks/monomyth.shtml
edit:
It fits in the pattern of stasis-change-stasis.
Before Anu and Padomay connected: stasis.
The first interplay: change
The gods become immortal: stasis
Mundus created: change
The Empire: stasis
The Oblivion crisis: change
Looks like we're gonna see some more change that will lead to the beginning of a new empire.