To explain my methodology for this Elden Ring theory, here's my following criteria:

But first, Disclaimer: My theory will be heavily based on Smoughtown's research and from his findings from other theorists, along with Ashen Hollow's Gloam-Eyed Queen Marika theory, and various sources of information on mythology that inspired the lore of Elden Ring itself. This theory will also involve heavy speculation but with logical conclusions based on in game events, character psychology, and inspirations for the lore. As for the rules:

Rule Number 1! - The safe assumption that the Greater Will is the creator god of Elden Ring (since it ties heavily into Nordic mythology and its sense of creation).

Rule Number 2! - Greatly distrust the history as written by the Golden Order, given the implications of how deceitful they are.

Rule Number 3! - Go by how the Greater Will's truly designs things for the order of things, not only as stated by word, but by environmental clues and in-game historic events.

Rule Number 4A! - Psychology is as important as physical evidence, study the actions of the characters and how they affected those around them, and keep special focus on if their actions contradict the authority of the Greater Will and how it results.

Rule Number 4B! - DO NOT mistake the Golden Order's authority for the Greater Will's.

Rule Number 5! - The theory will be presented as a timeline, keep in mind not to include something that would contradict how events would transpire.

Rule Number 6! - Have no sides or biases from the start, don't side with Ranni because she's pretty, and don't assume outright that the Greater Will and the Erdtree are parasites.

Rule Number 7! - Don't take my word as absolute, it is subject to change as new information comes forth.

I'll post the first part of my theory soon after Smoughtown comes out with his video on the dragons (the dragons are a critical piece to my theory). I'll see you soon when the time comes.