The Astral Plane, also known as the Astral Sea, was one of the planes of existence in various models of cosmology.
Astral Dominions
Within the Astral Sea laid the astral dominions, planes separated and unique from the surrounding fundamental plane but which owed their existence to it. Formed from the will of the Astral Sea's inhabitants the astral dominions were once linked into an intricate network within the World Tree. As a result of The Spellplague, the formerly bound planes drifted freely in the Astral Sea.
There were many dominions within the Astral Sea, the known ones being as follows:
Arvandor
Arvandor was the home of the elven pantheon, the gnomish pantheon, and several archfey. Corellon ruled over this good plane with his wife, the goddess Angharradh, while Garl Glittergold held his own, somewhat independent court.
Banehold
Banehold was the home of the Black Lord Unknown, who ruled from his keep the Black Bastion, as well as the gods who owed their fealty to him. The evil plane was surrounded by outlying wastelands that served as a warning to these subjugated deities.
Celestia
Celestia was an enormous mountain that contained three smaller peaks. The True Court was a city near the top of the mountain, from which Torm ruled the lawful good plane alongside Unknown and Bahamut.
Cynosure
Cynosure was a neutral meeting place of the gods and was usually closed and uninhabited. Cynosure was merely a stately meeting chamber full of high pillars and decorated with portraits of gods and goddesses both living and dead.
The Deep Wilds
The Deep Wilds was the home of Silvanus and his divine servants. The Deep Wilds were a vast expanse of untamed and wild wilderness, with no strong ties to any alignment but firm connections to several elemental realms.
The Demonweb Pits
The Demonweb Pits was Lolth’s domain and a former layer of The Abyss. This strongly chaotic evil plane was an immense and dark dominion of woven planar matter, at the center of which sit Lolth’s arachnid-shaped iron fortress.
The Dismal Caverns
The Dismal Caverns were a huge subterranean maze of natural caverns, ruled over by the solitary god Ghaunadaur. Other powerful entities, many aberrations touched by the Far Realm, also lived there, dwelling in the vast darkness that filled the plane.
Dwarfhome
Dwarfhome was the home of the dwarven deities and their worshipers, who dwelt underneath massive mountainous crags teeming with life. At the heart of Dwarfhome was the great hall called Erackinor, the residence of Moradin and his wife Berronar.
Eternal Sun
Eternal Sun was the dominion of Amaunator, Keeper of the Golden Sun, who shared the realm with Waukeen and his exarch, Siamorphe. Amaunator made his home in the Palace of the Four Suns, the central citadel of a golden city which was located amid shining, thriving lands and seas.
The Fugue Plane
The Fugue Plane was a flat and featureless plane with a ground of silvery mist. It was here that the god Kelemvor judged the dead, who arrived through the Shadowfell, either releasing them to the blessings of their god or sentencing them to eternal punishment.
Gates of the Moon
Gates of the Moon consisted of rocky islands that floated on and above a silvery sea, over which the moon waxed and waned constantly. It was here that the chaotic good greater goddesses Selûne and Sune both made their home, along with the goddess Tymora.
Green Fields
Green Fields was a place of rest, of lush valleys and hills ruled over by the Earthmother Chauntea. The halfling pantheon also resided here, moving from place to place like their mortal worshipers.
House of Knowledge
The House of Knowledge consisted of an ancient and tamed wood of giant oak trees and clear and fresh lakes and springs. A series of buildings throughout the dominion called the Library of All Knowledge was said to contain all the secrets of the multiverse.
The Nine Hells
The Nine Hells, or Baator as its denizens called it, was the home of devils and is ruled by Unknown, a former god-turned-archdevil-turned-god-again who resided in Malsheem, the Citadel of Hell. Eight other archdevils ruled eight other layers of the lawful evil dominion as vassals of Asmodeus.
Nishrek
Nishrek was home to the orc pantheon, ruled over by the savage god Gruumsh. This chaotic evil plane resembled a natural setting ravaged by eternal war, filled with of scorching deserts, jagged badlands, and dense and tangled forests, with black seas and rivers.
The Supreme Throne
The Supreme Throne was Cyric’s dominion but it was also a prison for the Prince of Lies, whose murder of Unknown had resulted in his internment for several centuries to come. The dominion was sealed off by the other gods, and none could enter nor could any leave.
Towers of Night
Towers of Night was the largest of the astral dominions, a vast and dark wasteland composed of mountainous regions, deserts of black sand, and malevolent seas, rivers, forests, and bogs. Ruling over this plane was the greater goddess Shar, who shared the neutral evil dominion with her servants Sseth, Talona, and Zehir.
Tu'Narath
Unlike the divine dominions where the gods reside Tu'Narath was a realm shaped by mortal minds, specifically those of the githyanki. Within the great metropolis carved from the corpse of a forgotten god the githyanki were ruled over by their lich-queen Vlaakith, who constantly plotted for the conquest of the other planes and who hold de facto control of the other nominally independent githyanki settlements.
Warrior's Rest
Warrior’s Rest was the dominion of Tempus, god of war and his nature shaped the plane into a landscape nearly as chaotic and unpredictable as the Elemental Chaos, constantly changing. The souls of warriors who worshiped Tempus or other human war deities lived here, always waging wars dying again and again in endless battle only to rise again while the victorious celebrated in the many halls that dot the landscape.
Geography
The Astral could be reached from almost any point in a Prime Material plane or first layer of any Outer plane by spell, psionic ability, or device. It was described as a barren place of other-dimensional nothingness extending in all directions. What little solid substance that floated in the bright, gray void was typically chunks of matter broken off from their original plane. The Astral had no gravity but objects did retain their mass so you could throw small items or push off from large objects to move in the weightless environment.
Time in the Astral flowed at the same rate on a Prime Material plane but the effects of time were slowed almost to a stop―a thousand years in the Astral plane felt like only a day to the traveler. Hence, it was sometimes considered effectively timeless. Creatures did not go hungry or age while in the Astral plane. For that reason, its mortal inhabitants needed to return to the Material Plane in order to have children or to reach adulthood.
Entering the Astral plane could be accomplished in one of two ways: projecting your astral form into the plane via the astral projection spell, or by physically entering the plane.Astral projection was the safest way to travel but still involved risk because you left your physical body behind on the traveler's plane of origin. The astral body would be accompanied by the astral forms of any items and clothing that were magical or radiated a magic aura. While projecting, your astral self was connected to your physical body by a silver cord that stretched out behind you for about 10 feet (3 meters), or 1 foot (30 centimeters) depending on the version of the spell, and then became invisible and intangible. Very few things could sever this silver cord: a powerful psychic wind, a githyanki silver sword, or the will of gods. The physical body left behind appeared alive but did not require food, water, or air and did not age. It could be moved and was vulnerable to damage and death. If the traveler's physical body was slain, death followed the projection some minutes later. If the astral self was slain, the traveler then returned to his or her physical body in a coma. Physically entering the Astral plane required a spell such as plane shift and brought travelers wholly into the Astral with no silver cord to anchor them to their plane of origin.