Thiasa sits at the center of the Planes. It is the most Earth-like of all planes and operates under the (mostly) same set of natural laws that our own real world does. It is roughly the same size as earth (perhaps 2% larger) and observes similar hours (24/day), days (364/year), lunar cycles, and seasons.
A silvery void that connects the Material World and Inner Planes to the Outer Planes, the astral plane is the medium through which the souls of the departed travel to the afterlife. A traveler in the Astral Plane sees the plane as a vast empty void periodically dotted with tiny motes of physical reality calved off of the countless planes it overlaps.
The Spirit World (also known as the Ethereal Plane) is a ghostly realm that exists as a buffer between the Material World and Shadow World, overlapping each. A traveler in the Spirit World experiences the real world as if they were an insubstantial ghost, and can move through solid objects without being seen in the material world. Strange creature imperceptible to material creature dwell in the Spirit World, many of which can extend their influence into the material world in mysterious and terrifying ways.
The eerie and deadly Shadow World is a grim, colorless “duplicate” of the Material Plane. It overlaps with the Material Plane and is in many ways is its warped and mocking “reflection”; one infused with negative energy and serving as home for dark and bizarre entities.
The Inner Planes contain the building blocks of reality and are the Plane that are in close proximity to the Prime Material Plane. Each Inner Plane is defined and dominated by a singular type of energy or matter. The natives of a particular Inner Plane are creatures either entirely adapted to the environment of made of the same energy or element as the plane itself.
Beyond the realm of the mortal world, beyond the building blocks of reality, lie the Outer Planes. Circling out from the Prime Material Plane like a vast clockwork orrery, it is to these realms that the souls of the dead travel, and it is within these realms in which the gods themselves hold court. The denizens of the Outer Planes form the mythologies of civilization, comprising angels and demons, titans and devils, and countless other incarnations of possibility. The Outer Planes are also the final resting place of souls from the Material Plane, whether that final rest takes the form of calm introspection or eternal damnation. The outer planes exist as solidified concept; as such, distances between them (and often time within them) are often matters of will and desire rather than distance and time.
Axis is a shining, symmetrical realm made of clockwork, crystal, stone and metal. Axis is a reflection of concepts such as Hierarchy, Bureaucracy, Order, and Progress. This plane has such things as electricity, railroads, and a thousand other marvels that won’t be available on the material plane for decades if not centuries. The plane also houses enormous libraries and museums. Lost writings, as well as myriad artifacts and relics from thousands of planes, era’s and places and stored within vast vaults and catacombs.
While no one race rules Axis, Axiomites, Inevitables, and other lawful neutral outsiders make their homes here, forever striving to expand their perfect city.
Eisadai is the realm of the Fae. While described as a Outer Plane, the realm has deep connections to nature and the Material World. In many respects it duplicates the Material World, but is far more idealized. Nature is more primal, shadows deeper, colors brighter, and its inhabitants far truer to their intrinsic natures (whether benevolent or wicked). Creatures of faerie originate here, and several races (Elves, Dwarves, and Gnomes among others) descended from fae ancestors.
A vast ocean of unrestrained chaos and untapped potential, the Maelstrom is the largest sphere and is said that from its unplumbed depths were born all the other planes, and to its anarchic deeps will all of reality eventually return. The Maelstrom responds to the whims of its inhabitants, and even beings of less than deific power have been known to transform themselves or carve out kingdoms using the power of the Maelstrom.
The confluence of too many stray and hidden dreams and desires are also reflected; as such, the plane is often bizarre, surreal, unpredictable, and dangerous.
Deeper into the plane, native Proteans cavort , creating and destroying the raw stuff of chaos with abandon.
Many souls are claimed by angels, deities, and fiends upon passing, but most will spend some time in The Underworld. This plane is comprised buildings and amphitheaters made of marble and stone in shades of black, white and grey. All souls whose final fate is still undecided are summoned here for their final judgment. Some are rewarded by being sent to the Plane they would be most comfortable in, others are sent to far off limbo’s to be imprisoned or hell’s to be punished. Others are simply reincarnated or granted life again if the situation warrants it.
The Underworld is home to the dualistic Aeons,and the enigmatic Psychopomps, and several Gods of death and judgment keep their diefic domains here as well.
The Dark Tapestry is the term for planets, worlds, and planes far beyond the edges of the known cosmology. Creatures native to the Dark Tapestry are often not subject to the laws of reality; in fact in many cases their very existence is a perversion to reality itself. These beings are governed by completely alien lords of unimaginable power and knowledge. Such creatures are too vast and inchoate to even notice visitors to their domain. Others take an interest in mortals, communicating with them through dreams and visions from beyond time and space. Many aberrant creatures are thought to be the servants and offspring of these unknowable entities.
This is a catchall category which describes all extra-dimensional spaces that function like a plane but have measurable size and limited access. The planes are theoretically infinite in size, but a demiplane might be only a few hundred feet across (or may be vast enough to almost be considered a full plane). There are theoretically a countless number countless demiplanes; while most are adrift in the astral or have gates to the Material, Shadow,or Spirit Worlds, some are cut off entirely from the transitive planes and can only be accessed by well-hidden portals or obscure magic spells. Deities and other powerful beings often use such places as private homes and estates, each reflecting the will and personality of its master. Such powerful beings frequently claim sections of the outer planes as well.