Early explorers from a forgotten Prime Material Plane learned the hard way that the spaces between stars harbored nothing but certain death, due to the abundance of Negative energies - an entropic effect that, derived from Chaos, gives power to the Undead. Stars, on the other hand, radiate Positive energies, derived from Order. Thus, interplanetary travel within any given Prime Material Plane proved impossible.
It was then, explorers of adventurous hearts turned to the Astral Plane as a means of conveyance. At first, travellers braved the Astral alone without modern conveniences - just an explorer and his Silver Cord; but this proved to be overly dangerous and impractical to nation-states. It was the invention of the Psychic Drive, a vat created lifeform that consisted of only a mind of intellect and Psionic power - yet subservient enough to be controlled by calculating machinery, that opened up the Multiverse to travellers and explorers from a myriad of dimensions and Prime planes. The Psychic drive could transport a physical vessel and crew to the Astral Plane, where travel time was literally at the speed of thought and, after some considerable mapping expeditions, other worlds could be reached. The nature of this nearly timeless travel was limited to orbital range, where time distortions did not affect the crew or the destination, thus aviation skills were still required to make this travel feasible.
Explorers also found that the Ring of Outer Planes was also accessible through the Astral, and some isolated gates and Color Pools also lead to Inner Elemental Planes as well. Entire Parallel Dimensions were laid open to intrepid explorers ... even travel through Time itself, though risky and potentially damaging to Order's Law, was possible with the right coordinates through the silvery Astral Seas.
The dangers of the Astral are many, through both natural weather patterns of the plane to denizens or even settlers of the Silver. Psychic Winds and Storms can set a Psychic Drive off course (or worse) and creatures such as the Githyanki can set upon travellers as pirates (or worse.)
The Northwind region is technically Pleiadian territory, though this means little to many of the entities inhabiting and claiming dominion to the world. Travellers coming to this world will be contacted by Pleiadian Guardians and be given a strict guideline of behavior on this world, enforceable through their considerable technology, Psionics, and extra planar contacts such as Archons and Seraphim. The Northwind region of this world has battlegrounds aplenty, seen and unseen by its inhabitants, that are being waged and the Pleiadians do what they can to limit non-Northwindic interference in the complex warfare on this world.