GOSSAMER, noun / adjective -- a fine, filmy cobweb seen on grass or bushes or floating in the air in calm weather, especially in autumn (like angel hair); an extremely delicate variety of gauze (like wedding veils); any light, thin, and insubstantial or delicate material or substance -- like the diaphanous curtains between all the worlds in the metaphysical universe, so easy to accidentally slip through. This is what happens to all the beings who first end up on a train to this anomalous world; these ethereal weak points in the curtainlike fabric of time and space shift them from their home worlds and land them in this six-part multiverse.
Its centrepiece - dubbed Hialao - is a tropical, hospitable, enormous modern realm; isolated though it does seem, like an island in the ocean, it is architecturally vital. A mysterious set of trains is able to traverse through hyperspace, connecting Hialao, like spokes on a wheel, to five other planes of existence: five different worlds created by the minds and needs of the countless people who come and go. We have Wildewall, the archaic land of wild and terrible nature and historical living; Elestis, the whimsical fantasy world overflowing with magic, colour, and karma; Parse, the epitome of all the futuristic, sci-fi, highly technological cities ever imagined; Barrows, a lawless mega-metropolis of dirt, crime and anarchy; and Tethya, an otherworldly Victorian-esque realm that is entirely subsea - underneath the ocean. Some newcomers choose not to settle down in any of them and are known as Drifters.
Each dimension advertises itself in an attempt to attract new citizens, and most have systems in place to acclimate the new arrivals to their new homes. Any attempts so far to understand the hows and whys of these worlds and how people end up here have been futile, and more terrifying yet is the inconstancy of it all; the denizens of this place can fall back into the aether as easily as they arrived, and as time goes on, the connection between all the worlds is proving to be more strange and dangerous. There has always been dissent and small power struggles, and disasters keep on unravelling; each dimension has its own troubles, monsters, threats of war, a peace that's as insubstantial as spun sugar and any promise that's ever been made.
With the dimensional displacements not yet showing signs of stopping, it's impossible to say who might arrive and what chaos they might cause. Whatever length of time they have in this already-collapsing series of fragile worlds should be well-spent.