The Astral Plane is the space between the Inner and Outer Planes, and coterminous with all of the planes. When a character moves through a portal or projects her spirit to a different plane of existence, she travels through the Astral Plane. Even spells that allow instantaneous movement across a plane briefly touch the Astral Plane. The Astral Plane is a great, endless expanse of clear silvery sky, both above and below. Occasional bits of solid matter can be found here, but most of the Astral Plane is an endless, open domain.
The Astral Plane is the great silvery sky that connects all planes to one another, the realm of pure thought and expanded consciousness. Occasional islands of solid matter float in astral space, but most of the plane is an enormous, seemingly eternal void of silver radiance.
As a gateway between the Inner and Outer Spheres, the Astral Plane teems with travelers, venturing between planes. Its nature as a crossroads makes the Astral Plane very dangerous. Although it’s possible to visit the plane bodily via plane shift or by using an item such as a robe of stars, most travelers prefer to play it safe by manifesting their souls in an astral body created by spells such as astral projection.
A creature’s astral body looks like a translucent version of its physical form, usually limned with a soft nimbus of blue or violet light. A slim tether of resilient incorporeal energy known as a silver cord connects a creature’s astral body to its unconscious physical body. If the astral body dies, the silver cord retracts into the physical body, returning the soul to its familiar seat (albeit at the cost of two permanent negative levels due to the resultant trauma). A silver cord resists most attempts to damage it, but if it somehow manages to break, the creature immediately dies, and the astral form housing its soul is cast adrift on the astral currents, pulled inexorably toward the enormous spire of Purgatory, which extends up into the Astral Plane from the surface of the Outer Sphere. As a realm of thought, the Astral Plane is home to entities that represent concepts, myths, and legends spawned from mortal thoughtforms. Mediums open their consciousness to these denizens of the Astral Plane, inviting them to reside in a physical form and spread their influence on the Material Plane.
Travel through the Astral Plane is a strange affair, as the plane’s subjective directional gravity means that each traveler chooses the direction of gravity’s pull. Creatures can move normally in any direction by imagining “down” near their feet and “falling” in that direction. In this way a creature “falls” 150 feet the first round and 300 feet on each successive round. Movement is straight-line only. A character can attempt a DC 16 Wisdom check to set a new direction of gravity or stop as a free action; this check can be attempted once per round. Any character who fails this Wisdom check on successive rounds receives a +6 bonus on subsequent checks until he succeeds. When moving in this manner, the traveler does not have the sensation of physical movement. Rather, the landscape of the Astral Plane (such as it is) seems to come toward, through, and past him.
The untethered astral bodies of the dead flow toward Purgatory along the River of Souls. During this process, the dross of mortality is shed, leaving behind only the soul’s core self, its memories, and the refined character of its prior life. Soul-collecting or soul-devouring predators such as astradaemons prey on the dead of the Astral Plane, usually limiting themselves to picking off isolated incorporeal Undead but all too often raiding parties of disembodied souls as they make their way toward eternity. The Divine One of death, hates this perversion of the natural order of the multiverse, and the entities known as psychopomps often act as guides to deliver souls safely to their final destinations.