Disclaimer : This is just how they work in my stories, I am no cosmologist or quantum engineer but I do enjoy reading about those fields.
In my stories universe, reality functions in an odd way, each reality is contained in it's own cosmic container in a larger container. Each reality is linked to each other in some way or another like being created because of another realities choices or directly interacting with another reality via magic, science or via souls going from one to another.
Most souls are contained in the space between these realities known as the Astral Plane. It is not a heaven or a hell, it's both. The space between realities varies as the size between realities is non-euclidan and can shrink and expand at any time. It is a very subjective plane as things can exist and not exist like a house being both a shotgun shack and a mansion at the same time but still being understood as a house to two different people. Some creatures are able to exist "physically" in the Astral Plane while others can only just visit it with spiritual bodies.
Magic is the ability to take energy from the Astral Plane without scientific equipment and use it for purposes like creating a fire while inside of a reality and not in the Astral Plane itself
The rules on magic are very loose as I am still writing them but souls are the main outlet of magic energy into a reality and can be contained in both the Astral Plane and a reality, in realities souls can be contained in what are called "mana crystals" which there are multiple types such as ones with souls that are active and can be recharged over time and ones that contain the energy of souls that have left the crystal. Of course as with any type of energy, the law of conservation of energy still applies to spiritual energy where it can only be displaced or turned into another type of energy. Black holes are one of the few ways that any type of energy is converted back into the subjective energy the Astral Plane is (mostly) made up of besides directly de-materalizing an object.
