Spirit World

The Spirit world is the place of the immaterial where Spirits Dwell.

This world is not of the material. It is a world of the mind and soul. Strength and power here are determined more by a strength of character and will rather than muscles or sorcerous talent.
The spirit world is not commonly accessible to living beings. Entering it while still alive is very difficult, and leaving it even harder.

The Border; Watching but unseen

The border of the spirit world is where all Souls first end up after death.
It is a desaturated vision of the material world and a spirit here can see the material world as translucent outlines, akin to a faded painting. They can move through these outlines without issue but cannot interact with them even if they wished it.
Spirits can linger at the border and behold the material world, unable to be perceived by beings on the material, but also unable to affect it. Spirits on the border are mere spectators.
Recently deceased mortals sometimes linger at the border of the spirit world, hoping some minor fissure would allow them entry and come back to life, or to observe the mortal world for just a while longer before moving on.

The Spirit world proper

The spirit world proper is the native realm of Spirits. Here they are strongest, where they feel at home.

A deceased soul or mortal visitor will want to travel from the border to somewhere in the spirit world. Most already have a destination in mind, or at the very least want to find somewhere better to be than the border. In order to get to such a destination they will have to travel through the spirit world and across the domains of the powers therein.

During the journey the traveler will encounter the inhabitants of these lands. Some will be benevolent to a traveler that might encounter them, however others are malevolent and would devour or do worse to any hapless soul they come across in their roaming. It is thus advised that one always be careful when confronting a being in the spirit world.

The Spirit wilds; Home of beasts

Between the domains of the various factions in the spirit world stretch out the spirit wilds; untamed lands that are most often perceived as forests, mountains, deserts and other forms of wilderness. They are filled with Anzu and other powerful spirit beasts and are thus often dangerous to travel through. Some of the creatures here are dangerous even to the very gods.

Spirit Domains

If one decides to wander through the spirit wilds they may come across one of the Spirit domains, such as Hades or Mount Celestia or the domain of one of the many gods.
Some of these realms can be found if one merely knows about them and intends to travel there. Some can only be found by the worthy. Some can only be found if you already know the way or have a guide that does.

Most gods have a domain in the spirit world, a place made for themselves and their followers. The gods will also often pass down instructions to their mortal followers via scripture on how to get to their divine domains once they die, or even send out their servants to collect the dead and bring them safely to their new home. Here those gods build themselves a paradise for themselves and their followers.
However other realms are built by dark gods for their own aggrandizemends, filled with souls stolen from other deities and forced to serve them.
Other domains are managed by multiple gods in a coalition and may take the shape of a city bustling with spirits while the golden palaces of the gods tower over everything.

The divine machine

At the very center of the spirit world is a giant palace of gold and steel the size of a hundred mountains. This is the Divine Machine and its representation in the spirit world.
It is here where the celestial bureaucracy is located, where orders are given that even gods have to obey.

Appearance:

The spirit world is split into many areas, from untamed lands where spirit-beasts roam over bustling cities where divine servants go about their duties, to shining palaces that serve as the homes of gods.
The appearance of the spirit world also changes depending on the expectations of the viewer.

Metaphysical but real:

The entire process of travel as well as entering or leaving these worlds is more of a mental endeavor than a physical one. The distances traveled aren't real, the borders of the domains are fluid and what is within them depends more on the visitor than anything else.
The visitor perceives the realms in such a way that it makes sense to them, physics and logic are important only insofar as they are important to the perceiver.

However that does not mean by being smart and thinking outside the box the spirit world becomes one's toy. Power is real. If a malevolent spirit confronts a traveler, their struggle might not actually be a contest of muscles and teeth but it does not mean the enemy can't simply be stronger, the traveler cannot be hurt or that the journey can't end in the stomach of an ancient predator.

Type

Dimensional plane