Where did you get that from?
About the Amulet's makers, from Intercept 7. About the material used, a hunch it's wrought of the material gained from the treaty between Ayleids and Daedra: creatia/magic.
Saying that it belongs implies that it should not be here. I haven't seen that anywhere else.
Where the Altmer sought to focus on dracochrysalis, or keeping elder magic bound before it could change into something lesser (and act which ironically required aetherial surplus), the Ayleids harvested castaway creatia from Oblivion by entering a pact with the masters of the Void, the Princes of Misrule.
Aether's run-off in Oblivion, harvested with the authority of the Daedra. You haven't seen it anywhere else, because I'm suggesting the creatia treaty represents a joint-rule of that creatia, between Ayleid and Daedra, and the lands congealed about White-Gold, using Oblivion's, harvested creatia.
I think that is a strange conclusion to reach. What even is a Convention ordering of the Aurbis?
The Dawn Era, when Akatosh's perch from eternity allowed lesser spirits to form and the new Mundus to form. Red Tower results from Convention, Aka's perch, stabilizing new Mundus and giving it Lorkhan's divinity.
After these two acts, which is commonly called the Convention, the gods left the earth.
Why?
The powers also created Red Tower and the First Stone. This allowed the Mundus to exist without the full presence of the divine. In this way, the powers of Ada-mantia granted the Mundus a special kind of divinity, which is called NIRN, the consequence of variable fate.
Because the Tower that stabilized Mundus without the presence of Akatosh was down, so the only way to preserve Mundus would be for Akatosh to return, as he had in the Dawn.
How are the souls of Emperors past the birth right of Dagon to Mudus?
What do you mean by "past" the birth right of Dagon, "takes precedence over"? Alessia's Covenant with Akatosh/Shezarr supersedes the right of Dagon to Mundus, as long as a http://www.imperial-library.info/content/oblivion-trials-st-alessia. By the time Martin has his chance to light the Fires, it's too late to, because Dagon's there. Instead, Aka reveals himself, as he had at Convention, reinforcing the barriers in the presence of divinity.
Edit: To sum what we see at the end of Oblivion - Martin mantling Akatosh - Mundus reverts to its last level of protection, against a fusion with Oblivion, and that's Ada-mantia Tower, or Convention.