The Vast Astral Expanse
This is a small compilation of all that exists in and beyond the Astral Seas and Wildspace.
The Astral Plane is somehow infinite and infinitesimal but is normally just considered a transitive plane to most other planes. It is also know as the plane were gods go to die. One my often find a "God-Isle" seemingly floating in space, breaking up the monotony of nothingness. Most travelers here use Astral Projection and are easily identified by their silver cords that keep them tethered to their point of origin. This allows them to return to their home planes and bodies. There are however some that call this place their home and as such do not have cords. These being are free to travel the vast emptiness to their hearts content. While there are a few humanoids such as Astral Elves, Giff, Githyanki, and Thri-kreen, there are also many Aberrations that call this space home.
Every world may it be solitary, or may it have neighbors (one or more suns, worlds, moons, asteroids, comets, or other bodies) exists in an airless void known as Wildspace. This neighborhood of celestial and planetary bodies is called a Wildspace system. In Wildspace, the Material Plane and the Astral Plane overlap. Creatures and objects in Wildspace age normally and are effectively on both of those planes at once. If one were to leave their world and continue outward until you neared the edge of their Wildspace system, they would begin to see a faint, silvery haze. By traveling into this haze, a party pass from Wildspace into the Astral Sea, more colorfully known as the Silver Void. The deeper into the Astral Sea a group travels, the thicker and brighter the haze becomes, but the stars that shine through it are always visible. Wildspace and the Astral Sea together comprise the Astral Plane the same as erath, air and sea comprise the Material Plane. The Astral Sea, like Wildspace, is a void; however, it is not an airless one. Here, creatures can breathe normally and exist indefinitely, never aging and never needing food or drink. Creatures can propel themselves through the Astral Sea with the power of their minds alone, though many astral voyagers wisely travel in well-armed ships, for fear of being attacked by frightening creatures or dangerous criminals or even pirates and warlords. *
In the current age: there is a secret war being waged in the Astral Seas. Much like how civilizations fight over control over the straights between major waterways, many are fighting to control the Astral Plane and the colorful portals to other planes that exist in it's vast emptiness. One such group are the collectives Aberrations known as the Illithids, or as they are more commonly known, Mind Flayers. Seen as a plague by most races, the Illithids are a Hive Mind race that seeks to spread it's control and influence across all planes of existence. As powerful psionics and consumers of living creature's brains, a coalition was formed ages ago to push them back. All that remains of that ancient militia are the Astral Gnomes. They lead the Gnomish Liberation Heavenly Force (GLHF) from "Asteroid Prime" in an attempt the find high level adventures to continue the fight against the Illithid forces.
*This paragraph pulled (and paraphrased slightly) from Page 4 of Astral Adventure's Guide