The Astral Sea

The Astral Sea is the domain of the mind. Powerful mages can use Astral Projection to leave thier unconcious body and inhabit a projection of their physical form in the Astral Sea. A wispy silver cord tethers them back to their body no matter how far they travel there.

A capable captain from the material world can also fly a Spelljammer craft up from the surface of the planet, through the atmosphere, and into the airless void of Wildspace. When nearing to the furthest reaches of wildspace, you would begin to see a faint, silvery haze. By traveling into this haze, you pass from Wildspace into the Astral Sea, more colorfully known as the Silver Void. The deeper into the Astral Sea you travel, 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 Astral Sea is not a sea, of course. It’s more like a fantastic version of outer space. It’s filled with vast clouds of a luminous, silver-gray substance that is not mist and not liquid. Stars glitter in the distance, especially in darker portions of the plane. Vast expanses of “open air”  between these drifting clouds provide travelers with hundreds of miles of visibility, and even in the middle of the densest astral mists travelers can see objects several miles away with ease—the stuff of the Astral Sea just doesn’t impede vision much at all.  In fact, vision in the astral seems to vary based on size or "concept" of an object or area, and certain talents may allow creatures to "see" farther than others.

Here, you can breathe normally and exist indefinitely, never aging and never needing food or drink. Floating in the astral doesn’t normally get wet or cold. A cool tingle on the skin is the only sensation. The astral is survivable in most areas, but cold and deadly in "thinner" areas.  Winged creatures can fly through the astral stuff as if it were air, and natural swimmers can swim through it as if it were water. Other creatures can move slowly by desiring to move.

By traveling through the Astral Sea, you can reach other Wildspace Systems, small astral realms, and even the Outer Planes, the planes of the Gods. 

Even though the Astral Sea is a three-dimensional void, it possesses a distinct astral horizon that forms something like the surface of an ocean. The mists below this surface are darker and denser, and those above it are brighter and more open. Most creatures and objects slowly orient themselves toward this subtle demarcation without even realizing it, and travel toward their destination along the “surface” of the Astral Sea. Two vessels meeting in the Astral Sea do so on this unseen surface, so that encounters begin in a space that seems more two-dimensional than it is. Similarly, a vessel approaching a large or significant location normally does so from the area’s equivalent of sea level, or from its equator in the case of locations that are shaped like worlds.

Distances in the Astral Sea are unthinkably vast, but most travelers need only journey for a day or two before finding a color strand leading to their destination. However, finding a specific place in the Astral Sea itself (for example, a particular githyanki stronghold) may take much longer. 

When starting from a known world or mote, travelers can search the local area for color strands leading to "adjacent" worlds. The number of astral conduits in the vicinity of a world or mote varies, because they fade in and out of existence. Generally, 1d3 -1 conduits can be found leading to adjacent worlds, and 1d2 -1 color strands leading to a distant world. It takes 1d6 hours to find a new color strand (if there's one to be found).

If a navigator knows of a recurring conduit, traveling that way is the fastest way to reach a destination. (its like the Bifrost Bridge ) Most conduits deposit a vessel a couple of hours or half a day (2d6 hours) from the world's location.

If the travelers do not choose to use a conduit, they may attempt sail across the astral in search of conduits, or attempt point to point navigation. While traveling along the astral horizon, there is a 50% chance of encountering a conduit each day.

Point to Point Astral Navigation

The above table assumes that the characters are traveling on a skiff of average speed or flying at average speed and are starting from a known world rather than the far astral. Use the skill of the character that is navigating. Add a day of travel time if the characters use one of the secondary options. If the characters are in a notably quick or slow vessel, subtract or add one or two days of travel time per travel time die, with a minimum of one day per die. Reduce a day (minimum of one) from the trip if the navigating character rolls a natural 20.