D&D General Independent Divine Domains: Story-wise, How would they be made/form?

[a--d]

Background
Came across something somewhere which claimed there are Divine Domains independent of any gods.
A number of them were listed. (Where? I forget.)
Inspired question: How were they formed?
Inspired question: Can they be formed?
Inspired question: If they can be formed, tricky balancing issues/power creep aside, what would their formation be like?
Also,
Inspired question: What is a Domain anyway?
Inspired question: What does Divine even mean?
-
So I'm asking you, story-wise (Or game-wise, I'm not picky.) What would the formation of a Divine Domain which was independent of the gods, and was in fact formed by the character themselves be like?
Especially if this character was just a normal person rather than half-god, blah, blah, etc like that.
If basically anyone could, form a Domain, Divine or otherwise, what comes to mind for how they would experience it?
-
...For that matter, what would a normal person who formed one be like?

 

[Redwizard007]

In previous editions, clerics could worship an ideal. Picture a world with no god of fire. Now imagine some crazy nut (like Trashcan Man from The Stand,) who is entirely obsessed with fire. Total pyromaniac. He burns everything that he can. Its not just a compulsion, but a legitimate spiritual experience for him. Somehow, this nut taps into primal forces that allow him to call fire out of nothing. Boom! New domain.