Within all of Creation, three things have remained a constant - The Three Realms. These Realms are where everything gets classified and shuffled into, as deemed by The Creator. Since the Beginning of Creation, the three realms that have existed were the Abyss, the Omniverse, and The Source. As such, while the Omniverse is the set that contains all, The Abyss and The Source exist completely outside of the concept of the Omniverse's Infinity Cycle. Throughout all of existence, there is only one Abyss and one Source. They go far beyond its laws, and are governed by its own set of laws and mechanic entirely.
The most mysterious of the Three Realms is The Source. This is where The Creator resides, and is completely inaccessible for all of existence; only The Creator can open gateways to and from it. As a result of this, what else might exist within the realm is unknown. Before the Deluge of Time, The Source and The Abyss were the only two realms to exist. As a result of it being unable to be explored, it is unknown what exactly presides in it aside from The Creator, or even what laws govern the supposed realm.
During the Omniverse Destabilization Crisis, a gateway was forced open utilizing a very elaborate loophole, only possible because of the Abyss’s Reboot Protocol. During that one instance, the Gateway looked different from traditional Abyss Gateways, and shone with various shades of blue. While The Source is closed off to all of existence, contacting The Creator is actually not impossible. All of the Existential Archetypes have a way to contact The Creator, and back at the house and workstation of Derxwna Kapsyla and R.K., their work computer, The Overseer, is able to contact The Creator. They choose not to contact The Creator, even though the option is available- though, Kalypsa Kapsyla has regular contact with The Creator, but even she knows little about them.
Because of the unknown state of The Source, it's presumed to be completely uninhabited, save for The Creator.
The next of the Three Realms is The Abyss, which is where the Existential Archetypes reside. The Abyss is a dark and desolate realm, though not devoid of its own form of life. Aside from being host to the Archetypes and the Abyssial Particles, the Abyss’s primary function is to serve as a repair facility for the Omniverse. When a Universe or a Timeline reaches a point of critical instability, it returns to the Abyss via a special Abyssial Gateway, where it prepares to undergo repairs. It also serves as a waystation for people traveling between the realms via normal Abyssial Gateways. The Abyss was the second of the Three Realms to exist, as it was The Creator’s first attempt to create a form of life and place for it to reside, while they themselves reside within The Source. It, like The Source, exists outside the Omniverse's Infinity Cycle, which means it is not part of the Omniverse concept itself.
Another way to think about the Abyss is this: While the Omniverse is All, the Abyss is it's antithesis in that it is Nothingness.
The lowest layer of the Three Realms is the core of the setting itself- The Omniverse. The Omniverse was The Creator’s second attempt to create life and a place for it to exist, and while initial attempts of it failed, it was when The Creator severed and sent out the Seron Crystal that the Omniverse “stabilized” and blossomed into an infinite existence. Given the name and implications, the Omniverse is the realm of infinite universes. It can be organized in its own hierarchical level, from the Omniverse down to the individual Timelines. Contained within are every event that could possibly happen, both the conceivable and unthinkable, as is the very nature of the term “infinite”- from the small quantum differences (smaller than even we can begin to imagine), to the largest realm-shattering changes, and so much further beyond. There is nothing that is not covered under the Omniverse’s all encompassing umbrella- aside from the lack of existence of the Omniverse and the Three Realms, as those were created by powers greater than the Seron Crystal’s unique properties alone.