I've been making my way through a box of stories, worldbuilding notes, and other strange things by a man named Rick Berkeley.
The world here, I think, is super interesting! I can see a lot of influence from Stephen King, H.P. Lovecraft, classic comics, and maybe even a little bit of the Cosmere? (though I don't think the timelines really line up with that.)
So far, Berkeley describes what seems, to me, to be a form of multiverse. Though dramatically limited from the multiverses I've seen in most popular media. This multiverse seems to contain no more than a couple dozen universes (Overspheres, Berkeley calls them). Each one, dramatically different from its cousins, belongs to one of four numina and sprouted at some point in the distant past, when a strange being (only referred to as "Firstlife" in the text) seeded mortality.
The purpose of these Overspheres, as far as I'm able to glean, is to foster Mortal Souls, though, as to what importance these have to the vast, cosmic entities above them, I couldn't possibly say.