Great Wheel cosmology

The Great Wheel is the cosmology in which the world of Toril was said to exist during the first and second editions of the Advanced Dungeons & Dragons game, although the actual term "Great Wheel" didn't mean the cosmology as a whole until the 3rd edition of the D&D game and its Manual of the Planes 3rd edition. In second edition, "Great Wheel" or "Great Ring" meant the Outer Planes only. The cosmology as a whole didn't require a name other than "the Planes" or "the Multiverse," as there weren't any formally named alternatives in the AD&D game.

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.

As it was described in first and second edition, the Great Wheel was 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. That was in first edition, long before the debut of the Planescape setting in 1994. On Hallowed Ground noted a number of alliances between the gods of Toril and those of other worlds, for example between the original Mystra and Wee Jas of Oerth. . In the novel Tymora's Luck, a plot by a god of Toril ends up involving the gods of Krynn. .

In 3rd edition, the Forgotten Realms cosmology was retconned, with the World Tree cosmology replacing the Great Wheel. No in-game explanation was given for the change, which 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 tells that Vhaeraun's realm is in the Carceri and Eilistraee lives in Svartalfheim.

Basic Structure
While the precise details of the Great Wheel cosmology changed to various extents throughout the first, second, third, and fourth editions of the game, as described in second edition it consists of a series of somewhat concentric spheres. In the center were the Prime Material Planes (Earth-like alternative worlds) each surrounded by an Ethereal Plane (misty realms of proto-matter). Outside of the Primes and Ethereals 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 Prime Material Planes to each other (bypassing the Ethereal planes) and also to the last sphere, the Outer planes. 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 Concordant Opposition.

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 can 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 are found on the equator between the boundaries of Fire, Earth, Water and Air (Magma is between Fire and Earth, for example). Four of the quasi-elemental planes are found between the boundaries of Positive Energy and the four elements (Steam is between Positive Energy and Water, for example). And the other four quasi-elemental planes are between Negative Energy and the four elements (Vacuum is between Negative Energy and Air, for example). The inner planes are surrounded by the Ethereal Planes, which also touch the Prime Material Planes and contain the various demiplanes.

Demiplanes, in second edition, are planes of finite extent found within an Ethereal Plane. They may be the creations of extremely powerful wizards, technologists, or demigods or they may be created when a large glob of proto-matter begins to pull away from its Ethereal plane and achieve separation. Demiplanes may eventually collapse in on themselves, re-merge with its parent Ethereal, or merge with an inner plane or Prime Material plane. Each demiplane has its own rules regarding gravity, vision, magic, and material make-up.

The Prime Material Plane touches both the Astral Plane and its Ethereal Plane, though these planes in the second edition cosmology do not touch one another. Though a single plane, the Prime consists of the countless crystal spheres of the Spelljammer setting, star-studded orbs that each contain a planetary system. Crystal spheres include 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.

Outer Planes
Many of the Outer Planes were divided into layers, infinite sub-regions that metaphysically overlap the other layers of the same plane.

Nirvana
Nirvana, also called Mechanus, 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 is filled with interlocking wheels 1000 miles (1600km) 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. 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
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 glows with its own color of soft light and each is 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
The Twin Paradises, also called Bytopia, was 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 (32km) 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
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
Occasionally called Arborea, Olympus/Arvandor is 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 is 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
Gladsheim, also called Ysgard, was between Chaotic Good and Chaotic Neutral in alignment and was the home of the Norse pantheon 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 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 there home here were Selûne, Sharess (in her aspect as Bast, Marthammor Duin, and Eilistraee. See the main article for more information on Gladsheim.

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 be an infinite number.

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
Tarterus, also known as Carceri, 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 visit this plane in the novel ''The Halfling's Gem.

Hades
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&mdash;everything was built onto or carved into the sides of these mountains and gravity was at a 45&deg; 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.

The Nine Hells
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, Caina, 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 were armies of the afterworlds would come to do battle. The four layers (Avalas, Thuldanin, Tintibulus, and Ocanthus) each consist 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
Concordant Opposition, also called the Friendly Opposition, the Outlands, Godsland, and simply the Land, is the plane of true Neutrality. Divine realms on this plane include the Caverns of Thought, Ilsensine's realm; the Court of Light, Shekinester's realm; Dwarven Mountain, which is 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. The planar metropolis of Sigil is believed to be the ring seen hovering over the infinite spire in the center of the plane.

Limbo
Limbo is the plane of Chaotic Neutral. Whether or not it has layers is the subject of some disagreement.

Fennimar is the realm of Fenmarel Mestarine. Knight's Rest is the realm of Tempus.

Pandemonium
Pandemonium is between Chaotic Neutral and Chaotic Evil.

The Towers of Ruin are the realm of Talos. Auril dwells in Winter's Hall.
 * Layer 1: Pandesmos

Hruggekolohk is Hruggek's realm. The Shattered Castle (also known as the Supreme Throne) is the realm of Cyric. Battle Guarde is the realm of Garagos.
 * Layer 2: Cocytus

Hidden Betrayal is the realm of the derro god Diirinka. The Unseelie Court is the realm of the Queen of Air and Darkness.
 * Layer 3: Phlegethon

Air
The Great Funnel is Akadi's realm.

Earth
The Great Mountain is the realm of Grumbar. The Cavern Under the Stars is the realm of Geb.

Fire
The Crimson Pillar is the realm of Kossuth.

Ooze
The Paraelemental Plane of Ooze, located between the planes of Earth and Water, is the home of Ghaunadaur's realm, the Cauldron of Slime.

Water
Sea of Timelessness is the realm of Istishia. The Murky Depths is the realm of Blibdoolpoolp. Shelluria is the realm of Eadro and Persana.