Cosmology

**Cosmology** is a branch of study concerned with the study of the universe: its origin, its evolution, its layout, and its eventual fate. It deals also with the study of planes of reality, and the planar barriers that separate the spheres of influence of each plane. The study of how the universe is structured is one of the greatest endeavours for learned individuals and arcane practitioners alike. Despite centuries of study, the questions have only led to theories, and though some definitive answers have been proven, much of the exact truth remains unknown.

When looking at the dimensions of reality, *cosmos* is taken as a dimension onto its own. In other words, in three-dimensional space that progresses over a fourth dimension (time), cosmos is a fifth dimension parallel to space and time that is also a fundamental part of reality. Just like space can change over time, so too can cosmos change over space and time, which means that different worlds can have different planar layouts and cosmologies that in turn change over and are affected by time.

## The Great Wheel

The Great Wheel is the prevalent cosmological model acknowledged by academia. It consists of a series of concentric spheres, each representing a new layer of reality and separated by planar barriers. In the centre is the Prime Material Plane, encased in a thick layer of arcane energy, called The Weave. Beyond that is the Aetherium, called also the Ethereal Plane, which forms a layer between Ygdren and the intertwined energies of Sol and Mor which make up the Planes of Limbo. Outside that are the Elemental Planes, commonly represented as a swirling hurricane that is in constant flux, stronger and more stable towards the inner parts, and devolving into the Elemental Chaos as it disperses. These planes include the four major elements (Fire, Earth, Water, Air), as well as segments in between where the elements intersect. Beyond the reaches of the storm is the Slip, which is in turn contained by the World Stream, a river of flowing arcana that sometimes coalesces into small pocket domains, called the Fractal Realms.

In this entire cosmology, all the planes are held together by a force that is commonly called Fate. Whether this force is fixed or everchanging as a result of external forces is a matter of great debate, however the fact that it exists is indisputable.

## Prime Material Plane

*Main article: Prime Material Plane*
The Prime Material Plane (also known simply as the *Material Plane*) is the central plane of existence, and the plane on which the physical known world takes form. Each world in existence is theorised to have at least the Prime Material Plane, which is typically equivalent to the world itself and given the same name.

In the cosmology of Ygdren, the Prime Material Plane is protected by a substantial planar barrier as well as a further barrier formed by the Weave. The prime planar barrier was weakened during the first Dread War, and later completely shattered in 4E 103 by Salakai at Lor Dulhir, allowing for an increased amount of arcane and planar influence to flood into the material plane.

## The Weave

*Main article: The Weave*
The Weave is a layer of arcane energy that has no physical form, but is theoretically an extension of the material plane. It is often depicted as a densely woven layer of threads of arcane energy, a blanket of sorts, slowly rotating around the material plane. These threads can be pulled into the physical material plane via the casting of spells on Ygdren. It is theorised that arcane energy from the material plane is ejected into the Weave during the same reactions inside stars that provides heat and light, having been converted from base energy forms into arcane.

In the cosmology of Ygdren, the Weave serves as both the main source of usable arcane energy and as an "atmosphere" of sorts. When particles of arcana hit this layer, they generally break up into arcane energy, though a sizeable enough amount can break through still intact. A skilled enough arcanist is in theory capable of forming planar tunnels from the Weave to reach the outer planes, though the required energy increases exponentially with each planar barrier that must be breached.

## Aetherium

*Main article: Aetherium*
Aetherium (also known as the *Ethereal Plane*) is a non-corporeal plane which exists as a mirror of the material plane, in which nothing is solid. It is theorised that the plane is formed as a by-product of unravelling arcana from the Weave, which causes a "shadow" effect of sorts of the material plane. In a physical example, if the Weave is a ball of yarn, this is the fuzz around the outside. The etherealness of the plane increase the further outward from the material plane it reaches, as it becomes less and less corporeal.

The inner regions of Aetherium, known as the *Border Ethereal*, are commonly accessible by arcanists practicing planar magic, as a sort of in-between state, but regions beyond that become more troublesome to traverse. Some creatures possess innate magic that allows them to fade into the ethereal plane and travel at will, but rarely do such creatures venture beyond the innermost borders of the plane itself.

## Planes of Limbo

*Main article: Planes of Limbo*
On occasion, base energy forms will be expelled beyond the Weave during the casting of powerful magic. These energy forms mingle with arcana during the expulsion, but will begin to slowly separate after passing through the Weave. Arcana is pulled one way, while base energy is pulled the other. Given the rotation of the Weave, which pulls the inner planes with it, energy further out becomes separated entirely by the growing force, but further in there is a perpetual swirling stalemate between Sol (a higher concentration of arcana) and Mor (a lesser concentration of arcana). In a physical example, the two are like liquids of different density that cannot properly mix, but are constantly being stirred.

Under very specific circumstances, the trapped energies here can form strange creatures made of pure energy, known as Archons. The exact type of the creature determines their form and behaviour. Archons born of Sol take radiant forms, desiring only to absorb arcane energy and grow. Archons born of Mor are the opposite, appearing as pockets of absence of light, desiring similarly to absorb base energy and grow.

## Elemental Planes

*Main article: Elemental Planes*
Physical matter from the material plane that passes through the Weave will generally travel quickly through the Planes of Limbo, driven by the energies there. However it typically comes to a halt just beyond it, gathering here at the edges of the inner planes to form a ring of matter clusters that are torn apart and remade by their turbulent orbit. Energy (arcane or base) that gathers enough force to expel out from the Planes of Limbo also collects here, adding to the concoction.

The outer regions of this plane, known as the *Elemental Chaos*, are bombarded by scattered pockets of arcane matter from the outer planes that collide with base matter and energy, causing intense elemental surges of magic that settle as they travel further inward, creating the relatively more stable elemental quadrants that characterise this place.

## The Slip

*Main article: The Slip*
The Slip is a region of cosmological space that is made of opposing forces to arcana. Where arcane matter is drawn together, the forces in the Slip push constantly outward, trying to escape the constraints of the inner and outer planes on both sides. This creates turbulent areas of intense pressure and force within the extents of this plane's boundary. Matter or energy of any sort that escapes the outer or inner planes is often trapped here, caught in the extreme conditions of this negative space, and occasionally jumbled all together into small hyper-condensed chunks of matter known as *slip cores*, or simply *cores*, which in turn can give birth to demons if they are ever pulled or thrown beyond the Slip and gather sufficient matter around them. The natural formation of such cores is akin to the formation of diamonds and other gemstones in areas of extreme pressure and heat beneath the surface of Ygdren. Cores can remain trapped in the Slip for countless millennia, which gives rise to the theories that primevals are created from particularly large cores that continue to draw in matter and energy to them in massive amounts.

## The World Stream

*Main article: The World Stream*
The World Stream is a river of chaotic liquid arcana that has condensed out of the Outer Chaos and become more tangible. It is a layer of torrential uncontrolled magic given physical form, orbiting the inner planes, kept together only by the sheer momentum of the current. The stream is interrupted only by small pockets of existence and spinning columns of arcane energy caught in eddies and swirls. The pockets are usually fashioned by extremely powerful entities, typically deities, or are an ancient by-product of the shaping of the world, remnants from before the cosmology took form.

## Fractal Realms

*Main article: Fractal Realms*
The Fractal Realms are fragmented pocket planes fashioned out of condensed arcana that is converted to base material forms through some type of immense power. They are typically the home of Prime or Ascended deities, and are often referred to also as *Divine Realms*. This name is however a misconception, as several Fractal Realms were not fashioned by deistic entities but instead formed over countless millennia during the shaping of Ygdren.

## The Outer Chaos

*Main article: The Outer Chaos*
A vast emptiness between the cosmos of different planets, filled only by scattered particles of gaseous arcana, moving at incredible speeds and colliding with one another to form clusters that may eventually become the cosmos of a different world.