Nine Realms Model
The Nine Realms Model is a WAAPT cosmological concept to describe the structure of individual universes in the multiverse. The Nine Realms Model is inspired by the cosmology of Norse myth and takes its name from it due to particular parallels, but is not a direct analogue of it.
Any given universe can be divided into nine realms, alternatively called worlds or planes. For the most part, separate universes (e.g. the OU and the AU) would each have their own versions of the Nine Realms.
The Material World
The Material World is the plane on which humanity as a whole resides. In the model, it is also referred to as Midgard, to tie into the Norse mythological equivalent. The Material World is also frequently referred to by several other names specifically in relation to other planes; "the waking world" in contrast to the Dream World, "the world of the living" in contrast to the Spirit World, "the human world" in contrast to the Feywilds, and "the mortal world" in contrast to the Hall of Origin, among other various names. In this sense, the Material World can be considered the "central" plane of the Nine Realms model.
The Material World can arguably be considered the domain of Zygarde.
The Feywilds are the domain of Xerneas. The Feywilds have not yet been explored in canon, but are described as "overflowing with life". In any universes where the Ultimate Weapon was constructed, Xerneas sealed himself and the Fairy-type in the Feywilds after the initial use of it, limiting contact with the Material World until the weapon was used again during the events of Pokemon XY.
The Spirit World
The Spirit World is the domain of Yveltal. The Spirit World is one of two "underworlds" in the Nine Realms model, being where most departed souls end up.
The Temporal and Spacial Worlds
The Temporal and Spacial Worlds are the domains of Dialga and Palkia. The Temporal World is described as a world of infinite diamonds, representing the flow of time itself, while the Spacial World likewise is described as infinite pearls, representing the expanse of space.
The Temporal and Spacial Worlds are theorized to be loosely tied to other versions of themselves in the multiverse.
The Distortion World
The Distortion World, also known as the Reverse World or the Torn World, is the domain of Giratina. It seems to be representative of antimatter, but something manages to prevent normal matter from annihilating the moment it comes in contact.
The Distortion World has been used as punishment for misdeeds -- originally, it was a prison for Giratina themself, and later became the final resting place of a large amount of the Ghost Lord's opposition, as well as a temporal prison for Cyrus. In this sense, it can be interpreted as a sort of "hell" analogue. As such, it's frequently referred to in swears, e.g. "damn it to Giratina's depths".
The Collective Unconsciousness
The Collective Unconscious is the vast sea of thought among all individuals, human or Pokémon, located roughly between the Dream World and the Material Plane. It is where the Mindscapes manifest, as well as Dashedreams. The Velvet Room exists on a subplane between the CU and the Material Plane.
The Collective Unconscious is possibly the domain of Azelf, Uxie, and Mesprit. The areas outside of Mindscapes are primarily inhabited by demons, a catch-all term for all beings created from the thoughts of sapient beings, taking the form of things including but not limited to historical figures, mythological beings, and other such ideas that enter the sapient consciousness.
The Dream World
The Dream World is the domain of Cresselia and Darkrai. It seems to be a sort of counterpart to the Collective Unconscious, being where one's mind goes when they fall asleep. It is one of the few realms that directly connects with other versions of itself throughout the multiverse.
In the OU, Cipher's experimentation on Cresselia caused the Dream World to start to collide with the Material World, but this was stopped by the J-Team.
The Hall of Origin
The Hall of Origin is the center of the domain of Arceus, and the home of all deity-level Pokemon. Although there is presumably more to the world than just the Hall, it is the only part mortals have glimpsed, in occasions such as the defeat of ▶▒_A▒ and other glitches.
The Entralink and Ultra Space act as gateways between the various realms, as well as to other universes. The Entralink channels through the Entree, the structural part of the Nine Realms Model that manifests to mortal eyes as a massive, twisting tree. Ultra Space, meanwhile, is a more direct, but uncontrollable path across the cosmos, channeling through Ultra Wormholes.
The Entree can be compared to Yggdrasil the World Tree in Norse mythology, while Ultra Space and the Ultra Wormholes can be compared to the Bifrost. Ultra Space can be considered the domain of Necrozma, as well as the home of the Cosmog line.
- The Feywilds were adapted in as a nod to Dungeons and Dragons. Although the Collective Unconscious is a concept developed originally by Carl Jung, the realm as it appears in WAAPT is inspired by Persona.