Cosmology of the Multiverse

Multiverse

Introduction

To begin with, each religious system has their own cosmology: both in micro (their Afterlife and creation of Prime Reality) and macro (the creation of entire multiverse) scale. However, even then, there are things that are simply common to all religions (and philosophies, since some of them try to dabble on that field), things that are believed to be universally true.
What must be said at the very beginning, is that actual truth is hard to discern. This is merely a rough sketch of what is known (or what is believed to be known). There is no way to know for sure, for majority of it lies beyond borders of science and reason. Even what we know might only be our own delusion, enforced on the universe. Or it might be a delusion of Gods: or their lie.
Many things are mystery. And most things will forever remain a mystery.

Multiverse

Many amateurs dabbling into magic makes a mistake of thinking that there are only two worlds: Our world (the Light) and the world of magic (the Dark).
Many amateurs dabbling into religious lore makes a mistake of thinking that there are three places: the Light, the Dark and their respective afterlifes.
Both claims are fundamentally true, and also far from being a full answer.
The universe is a spectrum, ranging from pure form of Light to pure form of Dark. Neither extreme is observable. Pure form of Light is impossible to be observed because an observer is made impossible - it would be a universe of pure materialism, with even most basic thoughs made metaphysically impossible. Pure form of Dark is impossible to be observed because there is no observer capable of witnessing it: it's purely abstract form, enough to drive any person foolish enough to observe it mad, or simply kill him by sensory overload.
Within that spectrum, there exist a vast number of vastly different places (though in case of some, 'places' would be more appropriate). Trying to make a map of a multiverse is pretty much impossible, at best one can more or less guess at what 'depth' a place like that is. And even that's a pretty general term.
The 'depth' can be roughly summed up to Shallow Light, Shallow Dark, Middle Dark Deep Dark and Outer Dark. Though every one of them has many alternative names in various cosmological traditions.
Shallow Light is a place where influence of Light is dominant. It's a highly hypothethical state: such an area would be dominated by laws of physics, but still connected to Dark strongly enough for a sapient species to exist. At least two of the known Remnant Realities is believed to originate in Shallow Light, but both... changed. Magic is impossible (or almost impossible).
Shallow Dark is a default state of the universe. Enough Light to be mostly stable and predictable. Enough Dark to allow existence of magic. All known Remnant Realities (save for few uniques) used to be this depth, just as Prime Reality does.
Middle Dark is a depth of domains and pocket dimensions of various Wild Daemons and other, religiously unaligned beings (or deities, divine beasts and so on). It's shallow enough to Shallow Dark to be 'mundanely' accessed, and deep enough to be able to ignore most of laws of the Light.
Deep Dark are realms where influence of Light is massively weakened, but it still exist enough to maintain at least semblances of causality and stability. It's a place where Gods reside, and place where their afterlifes are located: safely impossible to access by mortals (with very rare cases where it's not exactly the case), and infinite enough to be able to ignore most restraints of natural laws.
Outer Dark are hypothethical place that's so deep that no Light reaches it. It's simply too deep. Because of that, locations in the Outer Dark would be, by definition, not only inaccesible without losing your sanity (even a brief glimpse would be deadly) but also too abstract for one to understand (unless he is elevated into much higher state of existence). Some speculate that more abstract afterlifes, especially of monotheist religions like inrithism, are located here.

Locations

There is a vast ammount of 'places' in the multiverse, that are roughly divided into several categories. Once again, it has to be said, that there exist many doubts about majority of location types mentioned beneath.
Realities - In short: an expansive worlds (probably next to infinite, though the fact that they tend to be divided into planets doesn't help in exploration). They seem to be somehow divided from the so called Prime Reality (also known as Material World, Real World and under many other names): while their existence outside the Prime one is 99% sure, nobody knows if they actually exist within what we considered multiverse, or if they are something from an outside.
What's surely known is that they cannot be visited, nor contacted - it's only after they malfunction into Remnant Reality that they become accesable (mostly due to some catastrophic event that ends up creating a magical anomaly in Prime Reality, by parts of Remnant Reality bleeding into it). It's unknown if the Prime Reality is alone. There is even a theory that there is only a single Reality, with other worlds being a part of it (most likely as another planets).
Remnant Reality - Remnant Reality are remains of Reality - in most cases a single planet, but often merely a part of it - that underwent some devastating effect and stopped working. It's generally accompanied by an influence of the Light weakening, and the world itself collapsing into the Middle Dark. It's still unique, as while it is in Middle Dark, it's still heavily similar to average worlds.
Pocket Dimension - Quite common addon to Prime Reality. A small 'realm' connected to it, while residing in Middle Dark. They tend to be domain of daemons (wild daemons and so on). They are either directly accessable (for example a dungeons under an abandoned fortress, where something moved in and made them much bigger and more dangerous that they should be) or well hidden - here an example might be a house of local river nymphs, accessable 'through' the river, but only with their approval.
Dimensional Plane - A limited in size 'realm' of certain being/s. It has a defined size, defined form and defined rules. Tend to be almost never accesible unless their ruler wants one to.
Unreality - An entire reality-counterpart (endless in size) but in Deep Dark. Underworlds of various religions tend to be this, with their rules VASTLY different than rules of Light. Some might be composed of hundreds or thousands of lesser dimensional planes.