@Exmorri
Is the question of whether gods define or are defined by the world something Marble knows anything about?
I'm going to give official QM answers here to head off a lot of wondering later:
Belief does not define or change gods. In my experience, this is usually the main thing people are wondering about when they ask something like this. (Personally I think that idea is a dumb trope that needs to be deconstructed and die.)
If you spread a rumor that Alice the God of Music is also the God of Standing-on-one-leg-while-juggling-candles, and then start a secondary cult praising "Alice the God of Standing-on-one-leg-while-juggling-candles", nothing will happen to Alice except that Alice will receive a slightly increased fraction of prayers marked by the Divine Post Office with "We're not sure who these prayers are intended for, but our best guess is it's you". (Prayers function as a sort of currency.)
Now, for a sufficiently wide definition of '
the world', the world does define gods, because the world defines approximately everything.
Here's how it works: If you start a cult to some nonexistent god, for example the God of Striped Burlap Underpants, this will not create a god. Persistent worship of this nonexistent god will create a
position that the Celestial Bureaucracy will eventually notice and decide that if your cult is so dedicated to striped burlap underpants, maybe some unemployed minor god should be appointed as manager of that. "Bob, I hear your position as God of Backwater Hamlet #3428 is superfluous after that hamlet was razed by an invading army, how would you like a transfer to being God of Striped Burlap Underpants?" And then Bob will be invested with powers related to striped burlap underpants by his new boss the God of Undergarments. Who in turn works for the God of Clothing.
Transferred gods, particularly recent transfers, may retain trappings and powers and rights that they carried over from their old job.
Gods also trivially define the world in that they're intelligent beings with powers of their own they can use to act on the world. But gods are relatively low-agency compared to humans for various reasons, two of the biggest being 1) they are largely immortal so things are less urgent, 2) they have largely immortal bosses too so there's not much hope of a promotion. Instead, they mostly focus on doing their jobs of overseeing the world and making sure everything is working like it should. And playing office politics, naturally.