Natural philosophers and metaphysicists of the planet Tero and the greater Prime Material Plane have pondered and argued over the nature and structure of the cosmic planes for millennia, coming up with as many answers as there are people who have considered the questions. People who have found ways to visit the cosmic planes of alignment and return to the Prime Material have only made these questions harder to answer, as every individual seems to perceive something different on their journeys. Despite this, there are a few details that seem to run constant between every description of the planes. These constants can even be modeled and used to explain certain phenomena within the Prime Material Plane.
Most can agree that there are 5 main planes of existence, although there are many models which further divide these planes into more specific regions and sub-planes. The most general model, with only 5 planes, consists of the Prime Material Plane, associated with cosmic neutrality; Heaven, associated with cosmic good; Order, associated with cosmic law; Hell, associated with cosmic evil; and Pandemonium, associated with cosmic chaos. The latter 4 planes, known as the cosmic planes, ethereal planes, or even the holy planes, emanate from and intersect the Prime Material Plane in 4-dimensional space, creating a continuum of alignments which define and influence many aspects of life in the Material Plane. Despite being tethered to the Prime Material in many ways, the cosmic planes are not made of matter and exist outside of the flow of time. Residents of the cosmic planes are eternal, do not reproduce with each other, and do not create more of themselves. Unlike mortal residents of the Prime Material, the beings of the cosmic planes are bound to the cosmic alignment of their home plane. While they generally have free will within the bounds of their alignment, cosmic entities are incapable of acting outside of their alignment. Spirits and cosmic entities native to the Prime Material are often tied to specific items and places and are always neutral in alignment. Residents of the cosmic planes who find themselves near the borders of the planes may find that they under the influence of the nearby plane. This state will quickly revert once they get away from the border.
When a sapient mortal dies, their immortal soul leaves their body and is naturally drawn to whichever plane they were most aligned with at their time of death. Those who did not have a strong connection to any of the four alignments will be pulled back into the Prime Material Plane to be reincarnated with no memories of their past life. In general, those who find their souls drawn to one of the cosmic planes find that they enjoy where they end up, even if it seems distasteful to those of the other alignments. Each plane is someone's paradise, and very rarely do the souls of the dead not end up in an appropriate place. Souls that end up somewhere they don't like have very few solutions for their issue and they must usually rely on living people in the Prime Material Plane to help them. Getting in contact with living mortals to let them know a soul needs such assistance is easier said than done, unfortunately, and requires correct timing and planar alignment. More powerful planar beings have more inherent magical power and can communicate with other planes with relative ease. By this same token, these beings are also able to grant magical powers and abilities to mortals who meet certain requirements. With greater power comes a stronger tie to the cosmic planes, however, and the most powerful beings are completely incapable of leaving their home plane. This is not to say that travelling between the planes is easy. Crossing these barriers requires powerful magic and a solid understanding of the metaphysical structure of the universe.
The influence of the cosmic planes on the Prime Material grows and shrinks over time in different locations due to the rotation of the cosmic planes around the Prime Material. When a location is under the influence of one of the planes, it is easier to communicate with and travel to that plane from that location. The environment may also start to take on the traits of the associated plane, with nature itself seeming to gain an alignment. It is also worth noting that the cosmic planes do not literally orbit the Prime Material Plane. Any place in the material universe can come under the influence of a cosmic plane at apparently any time. This influence can go away just as quickly and mysteriously. At this point, the precise nature of the cosmic planes and how they relate to each other is unknown and may never be known. The planar diagrams presented here are nothing more than models, and most people who study this subject use both models of describing the planes to help explain certain aspects of the world. While there have been many attempts at a grand unifying theory of planar metaphysics, all of them fall short in one way or another and most people find themselves stuck with these incomplete models, as well as a few other useful planar models.
