The Astral Plane is one of the planes that comprise the Tetraverse. Its nature is dependent on the minds of the beings that inhabit it; in this way, it is like the Netherworld. Unlike the Netherworld, however, it is a plane of goodness and virtue. This is reflected in its inhabitants, known as the Astrals, who are benevolent.
The Astral Plane exists opposite the Netherworld in the Tetraverse; the two planes were created at the same time. The Ten Voidgods sought to bring an element of dualism into creation, and thus created the Astral Plane to be the positive side. They gave the plane a will of its own; from this will the Astrals were brought into existence. These beings serve the will of the Astral Plane (the "greatest good") to the best of their ability.
Unlike the dark and twisted Netherworld, the Astral Plane displays beautiful, poetic landscapes that are serene in nature. This appearance is a reflection of the minds of the Astrals and the other beings who have ascended to the plane. Unlike the Netherworld, who punishes those who are not native to the plane, the Astral Plane welcomes ascended beings and allows them the opportunity to shape their own part of it.
Due to the plane being one of the mind, physical laws are found to be lax within it. The domains of the Astrals are often dotted with cloud cities and floating castles; some of them don't have a "ground level" at all. Ascended beings usually shape their part of the plane to resemble dreams or fantasies they had while still in the Material Plane. As a result, the locales within the plane can differ greatly from one another.
The Astrals were the first beings to inhabit the plane. They were born out of the plane's will to have creatures who would serve as vessels for the greatest good; to this end, the Astrals are completely benevolent. There is no leader among them; they consider the plane itself to be their only true guide. They are equal in power to their evil opposites, the Archdemons, in terms of their own native plane. However, they also share the demons' weakness on the Material Plane, whose nature does not depend on the minds of its inhabitants.
Even more numerous than the Astrals are the Vanir, the first-seeded race of the Material Plane. This race of beings discovered the secret to ascension at the end of their millenia of civilization within the Material Plane. The last surviving Vanir exist within the Astral Plane and assist other beings who have ascended.
Although no other civilization as a whole has discovered the secret to ascension, there are certain individuals who have done deeds of extraordinary goodness and virtue; these beings' souls were recognized by the Astral Plane and allowed to ascend upon their physical deaths. Unlike the Vanir, who were prepared for ascension, these beings are often confused when they reach the plane. However, the Vanir are more than willing to explain to these lost souls what has happened to them and teach them about the nature of the Astral Plane.