Great Wheel Cosmology

The Great Wheel cosmology was the prevalent cosmological model in which the world of Toril was said to exist during the mid-14 century DR and the post-Second Sundering era. The Great Wheel was described as a complex, comparatively cosmopolitan place in which the gods of many worlds and pantheons mingled, the beliefs of many faiths and peoples bleeding together in a set of Outer Planes shaped predominantly by the polar forces of Law, Chaos, Good, and Evil. Thus it was that Lliira and the Greek goddess Hecate could feud over the love of the Sumerian god Enki and Work at a pleasure palace operated by the Aztec gods Xochipilli and Tlazoteotl. In fact, a number of alliances existed between the gods of Toril and those of other worlds, for example, between Mystra and Wee Jas of Oerth, as well as a plot by a god of Toril ending up involving the gods of Krynn.   The actual term "Great Wheel" did not mean the cosmology as a whole until the development of the World Tree cosmology in 1372 DR. By the Time of Troubles, the terms "Great Wheel" or "Great Ring" meant the Outer Planes only. During this time, the cosmology as a whole did not require a name other than "the Planes" or "the Multiverse," as there were no formally named alternatives yet.   By the late years of the 15 century DR, some sages began to use again the Great Wheel cosmology model, while other sages preferred to use the World Tree or the World Axis models. Of the three, the Great Wheel model remained the most commonly used; however, it was modified to include The Planes discovered after the Spellplague.  

Basic Structure

The Great Wheel cosmology consisted of a series of somewhat concentric spheres. In the center was the Prime Material Plane containing the Phlogiston with the Crystal spheres and worlds within, surrounded by an Ethereal Plane (misty realms of proto-matter). Outside of the Prime and Ethereal were the Inner Planes, also called the Elemental planes, which had their own structure based on a sphere. Then came the Astral Plane which connected the worlds in the Prime Material Plane to each other (bypassing the phlogiston) and also to the last sphere, the Outer planes. The Prime Material Plane touched both the Astral Plane and its Ethereal Plane, though these planes did not touch one another. The Outer planes, also called The Planes of Power, were 16 planes arranged in a circle (the Great Wheel) defined mainly by alignment and surrounding a 17th neutral plane known as the Outlands.   The Inner Planes were the six major elemental planes (Fire, Earth, Water, Air, Positive Energy, Negative Energy), the four para-elemental planes (Smoke, Ice, Ooze, Magma), and the eight quasi-elemental planes (Lightning, Steam, Radiance, Minerals, Vacuum, Salt, Ash, Dust). They could be thought of as being on the surface of a sphere with Positive Energy at the north pole, Negative Energy at the south pole and Fire, Earth, Water, and Air on the equator, equidistant from each other. The para-elemental planes were found on the equator between the boundaries of Fire, Earth, Water, and Air (Magma was between Fire and Earth, for example). Four of the quasi-elemental planes were found between the boundaries of Positive Energy and the four elements (Steam was between Positive Energy and Water, for example). And the other four quasi-elemental planes were between Negative Energy and the four elements (Vacuum was between Negative Energy and Air, for example). The Inner Planes were surrounded by the Ethereal planes, which connected them to the Prime Material planes.   Demiplanes were planes of finite extent found within an Ethereal Plane. They may have been the creations of extremely powerful wizards, technologists, or demigods or they may have been created when a large glob of proto-matter began to pull away from its Ethereal Plane and achieved separation. Demiplanes might eventually collapse in on themselves, re-merge with its parent Ethereal, or merge with an Inner plane or Prime Material Plane. Each Demiplane had its own rules regarding gravity, vision, magic, and material make-up.  

Transitive Planes

Ethereal Planes
  In the Great Wheel model, each Prime Material Plane had its own Ethereal Plane in which nothing was solid, including Living creatures, their possessions, weapons, and Armor. All Metal became ethereal Metal, flesh became ethereal flesh, stone ethereal stone, etc. The Ethereal touched its Prime at all points and bound it to the Inner Planes, but the connections were not abrupt transitions like to/from the Astral Plane but rather a gradual process in what was called the Border Ethereal. If you consider the Ethereal to be an ocean, a person in the Border Ethereal would be standing in the surf near the shore, Invisible to those on land but able to see them and their surroundings dimly. One could travel along the shore, staying in the surf, and step back on land at some other point or move away from the shore toward the Deep Ethereal. A curtain of vaporous color marked the transition between the Border Ethereal and the Deep Ethereal, and each plane had its own color. After traversing the Deep Ethereal and reaching the curtain of the correct color, you would pass through to the Border Ethereal of your destination plane.   By use of magic (or the natural ability that some creatures were thought to have, like phase spiders) one could fade into the Ethereal and travel at will. Gravity gave a sense of up and down, but movement in any direction was equally easy and objects released hovered in place. The proto-matter swirling about the Ethereal Plane could be used to create demi-planes, either through natural fluctuations in the medium or by the actions of powerful beings. The known Demi-planes at the time were the Demi-Plane of Shadow, the Demi-Plane of Time, the Demi-Plane of Electro-Magnetism and the possibly legendary Demi-Plane of Imprisonment.  
Astral Plane
  The Astral Plane was described as infinite nothingness interrupted only by small islands of material that broke off from their native planes and occasional spinning columns of astral conduits (called wormholes or gates and resembling water spouts from a storm at sea). The Astral Plane connected the various Prime Material Planes with each other and to the first layers of all the Outer planes. Travel in the Astral was usually accomplished by spell, psionics, device, or color pool and involved leaving your physical body behind while your astral self traveled to your destination. During this transit, a nearly unbreakable Silver cord connected your astral self back to your physical body. When you arrived at another plane, a new physical body manifested out of local materials. Wormholes linked specific places in the Outer planes to each other and to fixed locations in the Primes—quicker but likely more dangerous because your physical body was transported directly to a terminus that might be inhospitable or guarded.  

Outer Planes

The Outer planes were organized according to alignment, which is most easily visualized as a wheel with spokes radiating from the center of true neutrality. In the diagram below, planes associated with Good (sometimes called the Upper planes) are found above the line running from Nirvana to Limbo, and Evil-associated planes (sometimes called the Lower planes) are below. Planes associated with Law are found to the left of the line running from Elysium to Hades, and Chaos-associated planes to the right. Many of the Outer planes were divided into layers—infinite sub-regions that metaphysically overlapped the other layers of the same plane.  
Nirvana/Mechanus
Nirvana was the plane of lawful neutral. It consisted of only one layer where everything was in perfect order: equal parts Light and dark, heat and cold, and equal measures of the four elements. The entire plane was filled with interlocking wheels 1,000 miles (1,600 kilometers) or more in diameter slowly turning in synchronicity. Each disk had its own gravity extending in a sphere around it, enabling the surface(s) of the wheel to be inhabited. Mystra once made her home here and Helm's realm Everwatch, Psilofyr's realm Mycelia, Amaunator's Keep of the Eternal Sun, and Hoar's Doomcourt were all on this plane.  
Arcadia
Arcadia was between lawful neutral and lawful good in alignment, known for its trees. The trees of Arcadia grew in neat forests and regimented orchards. The bark was either Copper, Gold, Silver, or Iron, and the never-falling leaves ranged from dark green to fire red. The fruit from these trees had magical properties like potions when consumed. Arcadia had three layers, Abellio, Buxenus, and a third layer of which very little is known, including its name. See the main article for information about the inhabitants and features of Arcadia.  
Seven Heavens/Mount Celestia
Seven Heavens, also called the Seven Mountains of Goodness and Law, was the plane of lawful good alignment, home of the archons. Its seven layers (Lunia, Mecuria, Venya, Solania, Mertion, Jovar, and Chronias) were joined in such a manner that traveling deeper into the plane became an ascending journey, up mountain after mountain for example. Each layer glowed with its own color of soft Light and each was unique in terrain. The Seven Heavens were the home of Bahamut, Yondalla, and Moradin Dwarffather. See the main article for information on the seven layers and their denizens.  
Twin Paradises/Bytopia
The Twin Paradises were between lawful good and neutral good in alignment. The two layers (Shurrock and Dothion) were described as hanging upside down from each other about 20 miles (32 kilometers) apart (from sea level to sea level), sharing the same sky. Gravity was normal for each layer but in opposite directions. The Twin Paradises were the home of Garl Glittergold, Baervan Wildwanderer, Segojan Earthcaller, and Flandal Steelskin of the Gnomish pantheon. See the main article for descriptions of each layer.  
Elysium
Elysium was the plane of neutral good. The wide, slow-moving, and mostly navigable river Oceanus flowed through all four layers (from Thalasia to Belierin to Eronia to Amoria) and then on to the Happy Hunting Grounds. Most habitation was along the fertile banks of the river, diminishing farther away. Isis, Ishtar, and Enlil all made Elysium their home. See the main article for more information on the layers of Elysium.  
Happy Hunting Grounds/Beastlands
Outsiders called it the Happy Hunting Grounds, but the native wildlife, most of which were sentient and capable of speech, called it the Beastlands and didn't take kindly to being hunted. This plane represented the ideals of neutral good but tended toward chaotic good. Each of the three layers (Krigala, Brux, and Karasuthra) was vast and densely forested, but included habitats for all manner of natural creatures: mammals, birds, fish, reptiles, amphibians, insects, invertebrates, and their giant varieties. Skerrit the Centaur god made his home here as well as the Beast Lords. See the main article for information on the different layers and the "faces in the clouds".  
Olympus/Arvandor/Arborea
Occasionally called Olympus, or Arvandor, Arborea was the plane of chaotic good, home of both the Greek and Elvish pantheons. The two realms coexisted on the topmost layer of the plane at the pinnacle of their respective realms. The main feature was Mount Olympus, a huge mountain that linked the Greek part of the plane with the Prime Material Planes where they were strongest. This astral landmark also extended to at least one layer each of Gehenna, Hades, and Tarterus. This plane's three layers were called, in Greek/Elvish, Olympus/Arvandor, Ossa/Aquallor, and Pelion/Mithardir. Tucked away in a corner (so to speak) was the realm of Nephthys. See the main article for more information about this fascinating plane.  
Gladsheim/Ysgard
Sometimes called Ysgard, Gladsheim was between chaotic good and chaotic neutral in alignment and was the home of the Norse pantheon (of which Tyr was a member) which, despite a tendency to chaotic behavior, effectively seized control of the uppermost of the three layers. Their realm gives the first layer its name, Asgard, followed by Muspelheim and Nidavellir. Like Mount Olympus in Olympus, the main feature of this plane is Yggdrasil, the "World Ash", a tree that has roots and branches in the Prime Material Planes where the Norse gods are recognized as well as Niflheim in Hades. Forgotten Realms Deities that made their home here were Selûne, Sharess (in her aspect as Bast), Marthammor Duin, and Eilistraee. See the main article for more information on Gladsheim.  
Limbo
Limbo was the plane of chaotic neutral, home of the Githzerai and the Slaad. This plane was supreme chaos: a twisting, quicksilver place filled with bits and pieces of rocks, trees, the four elements, entire landscapes, strong winds, and random pockets of liquid, solid, or gas. Intelligent beings could subjugate the environment around them, causing the chaos to settle into forms of his or her desire. It was believed Limbo had five layers but they were all generally the same. Leira, Tempus, and Fenmarel Mestarine made their home here.  
Pandemonium
Pandemonium was the plane between chaotic neutral and chaotic evil in alignment and had no native inhabitants but many that were either immigrants, exiles, marooned, or prisoners. The entire plane was made of passages and caverns seemingly carved from solid Rock by the constant howling wind and wind-driven rivers. Demons and quasits lived or hid here and shadow demons were plentiful. Talos made his home here, and temporary visitors included Loki from Gladsheim and Loviatar of Gehenna. See the main page for more details on Pandemonium and its four known layers: Pandesmos, Cocytus, Phlegethon, and Agathion.  
The Abyss
The Abyss was the plane of chaotic evil, home of the demons and a seemingly limitless number of other foul Monstrosities. The stronger sought to dominate the weaker and the weaker conspired to overthrow the stronger. It was estimated the Abyss had 666 layers but it could well have been an infinite number.   Layers of the Abyss
The first layer was called Pazunia (after Pazuzu, who was most often found there) or the Plane of Infinite Portals, or the Palace of 1,001 Closets. It was a barren land of dusty deserts scorched by a red Sun. See the main article for information on the myriad layers of the Abyss.  
Tarterus/Carceri
The plane of Tarterus was located midway between chaotic evil and neutral evil in alignment. Each known layer of Tarterus is described as a chain of glowing scarlet orbs stretching into infinity. Each orb of the top layer is the size of a Prime Material world and the orbs get smaller with each successive layer. The orbs of the "inner" layers can be imagined as nesting within the orbs of the "outer" layers like Matryoshka dolls. See the main article for descriptions of the known layers of Tarterus. The Companions of the Hall visited this plane in the novel The Halfling's Gem.  
Hades/Gray Waste
Hades, also known as the Gray Waste, was the plane of neutral evil, home of the daemons. The three layers of Hades were Oinos, Niflheim, and Pluton. Pluton is sometimes mistakenly referred to as Hades. The layers of Hades were called glooms for good reason; they were realms devoid of emotion, hope, and peace—grey land and grey sky throughout, with no Sun, moon, or seasons to break the monotony. Here Anthraxus ruled in his Mighty Fortress, the Khin-Oin. See the main article for descriptions of the glooms and their denizens.  
Gehenna
This plane was midway between neutral evil and lawful evil in alignment. Each of the four layers (Khalas, Chamada, Mungoth, and Krangath) were composed of mountains and smoky, burning volcanoes with no bases or peaks—everything was built onto or carved into the sides of these mountains and gravity was at a 45° angle with the ground. Deeper layers had less heat and volcanic activity until you got to Krangath which had no natural Light or heat. See the main article for descriptions of the layers of Gehenna.  
Nine Hells/Baator
The Nine Hells, also known as Baator was the plane of lawful evil, home of the devils. The nine layers were: Avernus, Dis, Minauros, Phlegethos, Stygia, Malbolge, Maladomini, Cania (spelling changed in newer sources), and Nessus, and each extended infinitely in all directions and had its own physical laws and properties of matter. The barriers between layers connected the lowest points of the upper layer with points very high above the surface of the next lower layer, regardless if there was a structure (like a mountain or tall tower) there or not. Some infamous and powerful beings made their home in Baator, such as Asmodeus, Mephistopheles, Baalzebul, Belial, Mammon, and Tiamat. See the main article for descriptions of the Nine Hells.  
Acheron
Acheron was located between lawful evil and lawful neutral in alignment and was a place where armies of the Outer Planes would come to do battle in the Afterlife. The four layers (Avalas, Thuldanin, Tintibulus, and Ocanthus) each consisted of huge blocks of hard black iron-like material the size of countries that floated through air, joining for a time and then parting again. While blocks were touching, a being could move from one block to the next. Gravity pulled toward the center of each block. See the main article for descriptions of the layers of Acheron and the few who lived or visited there.  
Concordant Opposition/Outlands
Concordant Opposition, also called the Friendly Opposition, the Outlands, Godsland, and simply the Land, was the plane of true neutrality. Divine realms on this plane included the Caverns of Thought, Ilsensine's realm; the Court of Light, Shekinester's realm; Dwarven Mountain, which was the realm of Dumathoin, Vergadain, and Dugmaren Brightmantle; Annam's Hidden Realm, Semuanya's Bog, Sheela Peryroyl's Flowering Hill, Thoth's Estate, Oghma's House of Knowledge, Silvanus's realm of Summeroak, Gond's realm of Wonderhome, and Ubtao's Labyrinth of Life.  

Inner Planes

The four elemental planes—one each for Air, Fire, Earth, and Water—plus the two energy planes—one for Positive energy and one for Negative energy—made up the six major Inner Planes. Between each pair of adjacent elemental planes was a para-elemental plane. The eight quasi-elemental planes were found between the four elemental planes and the two energy planes. The four para- and eight quasi-elemental planes added up to twelve minor planes for a total of eighteen Inner Planes. Each plane was made up of primarily one type of matter, but pieces of other Inner Planes may have found their way in (or been brought in by powerful forces). One thing all Inner Planes had in common was that they were all hostile to lifeforms from outside, particularly from the Prime Material Planes.  
Elemental Planes
Elemental Plane of Air
This plane was the most hospitable to beings from the Primes because the substance of the plane was breathable and travel was fairly easy. The whole plane looked like the bluest sky on a summer day with only the occasional cloud or storm indicating the intrusion of some other element into the constant wind that was the Plane of Air. Pieces of solid matter floated in this realm and became home to other-planer creatures. The open space belonged to the air Elementals. Bahamut was thought to have a citadel here, as well as many other Deities of various pantheons. Akadi, the queen of free-willed Elementals was said to dwell in The Great Funnel, within a huge Maelstrom able to swallow the known world.  
Elemental Plane of Fire
The Plane of Elemental Fire was a hellish place, filled with all manner and color of flame from the candle to the white-hot glow of heated Steel, all burning without fuel and radiating Light and heat at maximum levels. Most unprotected matter was quickly consumed by the flames but pockets of other elements could survive in "cold spots" where the temperature was near that of a hot Prime Desert. The evil efreet and their fabled City of Brass resided here. Also the dwarf-like azer mined the basalt rocks that survived the heat for metals for their craft. Kossuth, the tyrant-king of the fire Elementals dwelt in his palace at the center of his realm called The Crimson Pillar.  
Elemental Plane of Earth
More inhospitable than even the Plane of Fire, the Plane of Elemental Earth was so solid that movement was nearly impossible unless a traveler could find a pocket of some less dense element or use magic to force an opening or permit them to walk through solid material. Without some protection, a non-native being would be caught like a Fly in Amber under tremendous pressure from the surrounding Rock and without air to breathe or Light to see. Inhabitants of this plane included xorn, crysmal, and the dao. Grumbar, the largest and most powerful Earth elemental, resided in The Great Mountain. Ogremoch, the prince of evil earth creatures, had his own flat-topped mountain inside the largest pocket of vacuum known to exist in the plane. The only deity from the Realms to make his home here was Geb in his Caverns Under the Stars.  
Elemental Plane of Water
An ocean without a surface, the Plane of Elemental Water had uniform pressure in all directions and felt like being several feet below the surface of a typical body of water in a Prime Material Plane, and indeed was illuminated with the same soft Light of that depth. The salinity of the water varied depending on proximity to the Negative Energy Plane—pure salt at the boundary with the quasi-elemental Plane of Salt, briny as you moved away, becoming pure and fresh in the middle, then getting warmer and more agitated as you approached the quasi-elemental Plane of Steam. Pockets of the other elements could be found here, but travelers that required air to breathe needed to make other arrangements. Inhabitants of this plane included water weirds, nereids, tritons, and the marid. Istishia made his home here in a realm called the Sea of Timelessness. The Murky Depths was the realm of Blibdoolpoolp. Shelluria was the realm of Eadro and Persana.  
Energy Planes
Positive Energy Plane
Also known as the Positive Material Plane and the Plane of Life, every atom of this plane vibrated with intense energy and produced Light across a wide spectrum. An unprotected traveler, if continuously exposed to the energies of this plane, would at first be healed of any wounds, then the cells of the body would quickly reach their maximum potential and then explode and become part of the plane, all in a matter of minutes. All non-magical or non-living material was quickly destroyed. The only known inhabitants of this plane were the inscrutable xag-ya which seemed mindless by Prime Material Plane standards, but must have had some intelligence because they could act as a local guide or a guardian when summoned to other planes. Where the Positive Energy Plane metaphysically intersected with the four major elemental planes, Air, Fire, Earth, and Water, it created the quasi-elemental planes of Lightning, Radiance, Minerals, and Steam respectively.  
Negative Energy Plane
Also known as the Negative Material Plane or the Plane of Death, everything in this plane sucked in all matter and energy creating a cold, pitch dark realm with structures made up of physical, solid blackness. Any unprotected visitor would quickly sicken, shrivel up, and die in mere minutes. Magical Light sources could barely penetrate the Darkness and non-magical material collapsed into dust and joined the black. Many undead drew their animating force from the Negative Energy Plane which allowed them to drain life force from the Living. The only known inhabitants of this plane were the mysterious xeg-yi, analog to the xag-ya in the Positive Energy Plane, and a species of "energy vulture" called the trillochs which may have originated on a demi-plane that got absorbed. Where the Negative Energy Plane metaphysically intersected with the four major elemental planes, Air, Fire, Earth, and Water, it created the quasi-elemental planes of Vacuum, Ash, Dust, and Salt respectively.  
Para-Elemental Planes
Para-Elemental Plane of Smoke
Between The Planes of elemental Air and elemental Fire was the plane of para-elemental Smoke, also called plane of Ash or the Great Conflagration. It appeared as a cloud of foul-smelling fog which got a little more pleasant as you approached the plane of Air, or hotter and more luminous as you moved toward the plane of Fire. Smoke particles made breathing difficult to the point of asphyxiation so travelers needed to be prepared or death was delayed only as long as you could hold your breath. Pockets of Air were a welcome relief. Pockets of Fire looked like free-floating fireballs. Using the sphere model discussed above, the para-elemental plane of Smoke touched The Planes of Air, Fire, Lightning, Radiance, Vacuum, and Ash, and could be reached directly through the Ethereal Plane. Ehkahk, the Smoldering Duke, lived in the Choking Palace and proclaimed himself ruler of the smoke mephits.  
Para-Elemental Plane of Magma
Between The Planes of elemental Fire and elemental Earth was the plane of para-elemental Magma, also known as the Fountains of Creation. It was a long sea of molten lava that thinned out and became gaseous toward the plane of Fire, or thickened until it became solid Rock toward the plane of Earth. Breathing difficulty went from bad to worse in the same manner. Pockets of Fire would be bubbles of elemental Fire and the thin gasses from that plane. Pockets of Earth were pillars of granite or rough-cut stone floating in the magma. The para-elemental plane of Magma touched The Planes of Fire, Earth, Radiance, Minerals, Ash, and Dust, and could be reached directly through the Ethereal Plane. Chilimba, First General of the Cauldron, Master of All Mephits, claimed rulership over the entire plane from his stronghold Caldera.  
Para-Elemental Plane of Ooze
Between The Planes of elemental Earth and elemental Water was the plane of para-elemental Ooze, also known as the Swamp of Oblivion. Close to Earth the rocks and dirt took on a clammy dampness. As you moved toward Water, the density decreased to a quicksand-like state and then thinned out to muddy silt. Spells and devices that provided Water Breathing capability worked in this plane also. Pockets of Water would form an irregular bubble in the muck. Pockets of Earth were solid nuggets suspended in the ooze. The para-elemental plane of Ooze touched The Planes of Earth, Water, Minerals, Steam, Dust, and Salt, and could be reached directly through the Ethereal Plane. Ooze was the location of Ghaunadaur's realm, the Cauldron of Slime. The only other name that survives in lore related to this plane is Bwimb, another possible prince of para-elemental evil.  
Para-Elemental Plane of Ice
The plane of para-elemental Ice, also known as the Frostfell, was found between The Planes of elemental Water and elemental Air. Scattered icebergs marked the border with Water, eventually becoming solid ice broken by fissures and caverns until finally jutting into the plane of Air as ice cliffs. This plane shared the restrictively solid nature of the plane of Earth. Inadequately protected travelers would soon find themselves preserved for all time in sheer ice. Pockets of Water took the form of an underground lake while pockets of Air would form ice caverns of any shape or size. The para-elemental plane of Ice touched The Planes of Water, Air, Steam, Lightning, Salt, and Vacuum, and could be reached directly through the Ethereal Plane. Cryonax, the prince of evil cold-using creatures, built his massive castle of ice, Rock Crystal, and glass on this plane and named it the Chiseled Estate.  
Quasi-Elemental Planes
Positive Quasi-Elemental Planes
 
Quasi-Elemental Plane of Lightning
Where the Positive Energy Plane intersected with the plane of elemental Air, it created the quasi-elemental plane of Lightning, also called the plane of Storms, the Vengeful Land, or the Great Illumination. At the border with Air was a continual thunderstorm with a constant barrage of lightning bolts arcing between ominously dark clouds. The atmosphere was filled with the sharp tang of ozone and a deafening cacophony of thunderclaps. All form of electrical discharge could be found here: lightning bolts, ball lightning, sheet lightning, static shocks and the gentle glow of St. Elmo's fire. It is said that quasi-elemental creatures cavorted amid the chaos. At the border with the Positive Energy Plane stood the mysterious Tower of Storms, gateway to a continuous torrent of electrical power that issued from a wall of pure brilliance. Following the sphere model discussed above, the quasi-elemental plane of Lightning touched The Planes of Positive Energy, Air, Radiance, Smoke, Steam, and Ice, and could be reached directly through the Ethereal Plane.  
Quasi-Elemental Plane of Radiance
Between the Positive Energy Plane and the plane of elemental Fire was the plane of quasi-elemental Radiance where all manner of flame and fire burned at its brightest and hottest. Every color of combustion could be found here in a dazzling display seen nowhere else, and the creatures were equally brilliant. As you approached the Positive Energy Plane, spheres, walls, and lines of prismatic force crisscrossed the plane as the Light became sharper and more crystalline until finally blending into the coruscating whiteness of blinding intensity that indicated you had reached the border. Standing at the border was a tower of blue Light called the Heart of Light that was rumored to be a place of great healing. In addition to the precautions necessary to travel the Plane of Fire, eye protection was needed to prevent permanent blindness while in this plane. The quasi-elemental plane of Radiance touched The Planes of Positive Energy, Fire, Lightning, Smoke, Minerals, and Magma, and could be reached directly through the Ethereal Plane.  
Quasi-Elemental Plane of Minerals
Between The Planes of Positive Energy and elemental Earth was the plane of quasi-elemental Minerals. Upon crossing the border from the Plane of Earth, the entropy-fighting influence of the Positive Energy Plane manifested in growing veins of Crystal and metal-bearing ore permeating the Rock, which itself became black Marble. All manner of gems and metals aggregated in their pure forms and laced the Marble, becoming increasingly fragile and vibrating with energy until finally shattering at the fluctuating cliff-face border with the Positive Energy Plane. Near the border was the Tower of Lead, said to contain the most magnificent forge in the multiverse, where master craftsmen sometimes would risk death to perfect their art. In addition to all the difficult and deadly conditions of the Plane of Earth, this plane presented even more challenges. Sharp crystalline edges could cut travelers not native to this plane or elemental Earth as they passed through. Likewise the delicate insect-like inhabitants were beautiful jeweled creatures with sharp angular features. By far the greatest danger to any being not native this plane was fossilization. The longer one stayed in this plane, the greater the chance the forces acting on the minerals would turn you to stone (if you were lucky) or transform you into Crystal, gemstones, or gold-veined granite. Magical protection from petrification did not prevent fossilization. On top of that, any Crystal that formed in the intense pressure and zero gravity of the Plane of Minerals was almost certain to Shatter when brought into a plane with gravity and normal atmospheric pressure. The quasi-elemental plane of Minerals touched The Planes of Positive Energy, Earth, Radiance, Magma, Steam, and Ooze, and could be reached directly through the Ethereal Plane.  
Quasi-Elemental Plane of Steam
Where the Positive Energy Plane intersected with the plane of elemental Water, it created the quasi-elemental plane of Steam. The temperature of this plane varied from cool to near boiling, creating the conditions for all varieties of mist, fog, and vapor. The entire plane was suffused with a soft glow which eventually became a brilliant glare at the border with the Positive Energy Plane. Near the border was the strangely named Tower of Ice which was used by alchemists as a laboratory to enhance Potion brewing. Air-breathing, lung-using creatures found it difficult to get enough air from the muggy water vapor and were effectively slowed by water gathering in the lungs. Overall, this was the most hospitable of the Positive quasi-elemental planes. Using the sphere model discussed above, the quasi-elemental plane of Steam touched The Planes of Positive Energy, Water, Minerals, Ooze, Lightning, and Ice, and could be reached directly through the Ethereal Plane.  
Negative Quasi-Elemental Planes
Quasi-Elemental Plane of Vacuum
Between the Negative Energy Plane and the plane of elemental Air was the plane of quasi-elemental Vacuum. As in other Inner Planes, standard physics did not apply to this plane; as the air got thinner moving toward the Negative Energy Plane the temperature and pressure remained the same even when the region of perfect vacuum was reached—there was just nothing there. Spells that offered protection from the elements did not protect from the lack of all elements. Even beings from neighboring planes could not survive for long as they began to consume their own essence to stay alive. The ambient Light radiating from the Plane of Air faded to absolute black at the border with the Negative Energy Plane, and there is where the Doomguard built a structure called Citadel Exhalus, Portal of the Last Breath. Creatures of Invisible force flitted through the gloom, but for what purpose no one has ever discovered. The quasi-elemental plane of Vacuum touched The Planes of Negative Energy, Air, Smoke, Ash, Ice, and Salt, and could be reached directly through the Ethereal Plane.  
Quasi-Elemental Plane of Ash
Between The Planes of Negative Energy and elemental Fire was the plane of quasi-elemental Ash. Moving from the Plane of Fire, the last embers died out leaving the cold remnants of combustion hanging in the gloomy atmosphere. The temperature dropped quickly to a bone-chilling cold, all Light from the Fire plane was rapidly blocked from view, and the ash steadily thickened toward the Negative Energy Plane until it ended in a gray wall in the Darkness at the border. Vision was limited and breathing impossible without assistance of some sort. This plane would leech the warmth out of any creature with a body temperature above freezing, especially natives of Fire, Smoke, and Magma which would die in a matter of minutes. Creatures of Ash shunned warmth because their bodies could explode into lumps of ash if brought to room temperature. Another of the Doomguard's strongholds, the skull-shaped Citadel Cavitius, was here at the border with the Plane of Death, but it was taken over by the Lich Vecna long ago. They subsequently built a replacement and named it the Crumbling Citadel. The quasi-elemental plane of Ash touched The Planes of Negative Energy, Fire, Magma, Dust, Smoke, and Vacuum, and could be reached directly through the Ethereal Plane.  
Quasi-Elemental Plane of Dust
Where the Negative Energy Plane intersected with the plane of elemental Earth it created the quasi-elemental plane of Dust, home of the dune stalkers, sandlings, and sandmen. From the border with the Plane of Earth, the earth and Rock cracked and split into smaller and smaller pieces, losing cohesion and variation until nothing was left except fine sand. At the same time the pressure experienced in the Earth plane was reduced to normal but there was still no breathable atmosphere. Continuing on, the grains got finer and farther apart, the empty blackness between the dust motes grew until finally all motes dispersed and only Negative Energy was left. Here the Doomguard built their favorite tower, the Citadel Alluvius. The disassociation and dispersal properties of this plane acted on anything solid that lacked protection. In a matter of minutes, non-native items and creatures, including beings from neighboring Inner Planes that were at least partially solid, would break down and drift apart long past the point where life was sustainable. The quasi-elemental plane of Dust touched The Planes of Negative Energy, Earth, Ooze, Salt, Magma, and Ash, and could be reached directly through the Ethereal Plane.  
Quasi-Elemental Plane of Salt
Between the Negative Energy Plane and the plane of elemental Water was the plane of quasi-elemental Salt. Entering this plane from the Plane of Water, the brine overwhelmed the merely salty water and quickly solidified into hard crystalline lumps of salt. All water was soon absorbed or evaporated and the lumps joined to form a solid block of salt which continued until it ended in a great cliff overlooking the Negative Energy Plane. At the border, carved out of the salt cliffs, was the Doomguard stronghold Citadel Sealt. All unprotected beings containing water quickly dehydrated until their desiccated remains were encased in salt. Denizens of this plane feared water in any quantity because it would start to dissolve them or violently Shatter them if immersed. The quasi-elemental plane of Salt touched The Planes of Negative Energy, Water, Ice, Vacuum, Ooze, and Dust, and could be reached directly through the Ethereal Plane.  
 

Revision

When sages of the late 15 century began to use the Great Wheel model again, they revised it to include the new planes discovered after the Spellplague and normally associated with the World Axis model.   The Elemental Chaos was considered to be the farthest extent of the Inner Planes, a hostile and unknown plane where all the elemental planes were combined. Some speculated it was home to strange Elemental Creatures.   The Feywild and the Shadowfell were considered to be parallel planes to the Prime Material, extreme echoes of the worlds of the Prime much like in the World Axis model. Those planes replaced the Plane of Faerie and the Plane of Shadow of the earlier version of the Great Wheel model.   Appendix Notes   Ed Greenwood created the Faerûnian pantheon by choosing Deities from the first edition Deities & Demigods book, sometimes renaming and modifying them, with the aim of ending up with one deity for every Outer Plane or Outer planar layer in what we now call the Great Wheel cosmology. In this sense, the Faerûnian pantheon was created with the Great Wheel in mind.   That was in first edition, long before the debut of the Planescape Campaign Setting in 1994, which offered alternative names for many of The Planes.   In 3rd edition, the Forgotten Realms cosmology was retconned, with the World Tree cosmology replacing the Great Wheel. The in-game explanation for the change was given in Die, Vecna, Die! which marked the end of the 2nd edition cosmology: "Even with Vecna's removal, his time in the crux effected change in superspace. Though the Lady of Pain attempts to Heal the damage, the turmoil spawned by Vecna's time in Sigil cannot be entirely erased. Some Outer Planes drift off and are forever lost, others collide and merge, while at least one Inner Plane runs "aground" on a distant world of the Prime. Moreover, the very nature of the Prime Material Plane itself is altered. Half-worlds like those attached to Tovag Baragu multiply a millionfold, taking on parallel realism in what was before a unified Prime Material Plane. The concept of alternate dimensions rears its metaphorical head, but doesn't yet solidify, and perhaps it never will. New realms, both near and far, are revealed and realms never previously imagined make themselves known. Entities long thought lost emerge once more, while other creatures, both great and small, are inexplicably eradicated. Some common spells begin to Work differently. The changes do not occur immediately, but instead are revealed during the subsequent months. However, one thing remains clear: Nothing will ever be the same again." This event shifted the realms of many Deities around to group them by pantheon or theme rather than alignment. Nonetheless, planes of the Great Wheel continued to receive mentions in official products. For example, in Sacrifice of the Widow, Cavatina Xarann tells that Vhaeraun's realm is in Carceri (Tarterus) and Eilistraee lives in Svartalfheim. The Player's Guide to Faerûn still uses the terms Inner and Outer planes even though they are no longer thought of as concentric spheres.   In 1994 the Planescape setting collapsed the alternate Prime Material planes into a single plane consisting of the countless Crystal spheres of the Spelljammer setting, star-studded orbs that each contained a planetary system. Crystal spheres included Realmspace, which contained the Forgotten Realms setting; Greyspace, which contained the Greyhawk setting, and Krynnspace, which contained the Dragonlance setting. The spheres were surrounded by the Phlogiston, a many-colored chaos that was considered beyond the power of the gods.   Although there is no in-game explanation for the addition of those planes to the Great Wheel, it has been said by 5th-edition developers that the cosmological models described in the 5th-edition's Dungeon's Master Guide are creations of sages of diverse mortal worlds, implying that the Great Wheel was revised at some point.
Map of the Planes

Great Wheel Cosmology

Table of Contents