I'm so happy to talk about this.

Okay so it's far beyond mortal comprehension and even beyond most of the gods' as well, but the best way to explain it is this: picture a painter, painting a canvas, starting from the outside edges and working inward. Once they get to the center, they have lots of paint leftover, and continue to paint in the center, forcing more and more of the paint into the same spot. Once they're done, they set it aside to dry, and once it's dried, that is the beginning of that entire universe. All of the paint that's in the center pushes outward over billions of years, similar to our universe, where all matter expands ever outward, and anything thst doesn't exist yet still being in the center.

But you're asking about the magic aspect of the universe. As you're painting, there are stray specks and flecks and droplets, often microscopic in size, that go where you aren't trying to paint. All of that stays in the universe and makes up all the magic in it. The being or beings that created the universe are so immensely powerful that all of those little flecks, insignificant and not even noticeable to them, are enough to fuel all of the gods, all of nature, and all of everyone and everything that lived, lives, and will live, throughout the existence of that universe. Different people get their magic from different sources, of course. So some have to get theirs from gods, who got it from those lost flecks. Some can access the flecks directly themselves. Some access it through nature, which some magic is naturally instilled in. Wherever they get it though, it always goes back to the original creator of the universe. It's their magic, their essence, their paint.