On the Crossworld side, however, things are far different. The appearance of the portal is determined by the nature of reality in that Crossworld. Portals may be doors, black holes, mystic loci, archways, or anything else that the reality contains, including being eaten by a demon. They move frequently and unpredictably, and when searched for are rarely found. Instead, they are often discovered by accident, and often the person crossing through doesn't know what is happening. The wanderers and explorers, the misfits of society, are the ones who most often encounter the portals; very rarely does a person reach Crossroads who is not drawn by it.
The exact nature of the portals and where they came from isn't known to anyone, not even the inhabitants of Crossroads. In the Crossworlds, they can be totally unpredictable, and even in Crossroads they will occasionally do something that no one can explain. Many believe that they are sentient, but if so, it is a sentience unlike anything else ever encountered.
Crossroads stories will be interacting with Crossworlds, both new ones created by Crossroads authors and others that are already established universes, but only with the consent of the creator(s) of the Crossworld. Crossroads itself is a joint project, but any Crossworlds are under the sole control of their creators.
Also, whether or not Crossroads stories will be told about a particular Crossworld is at the discretion of that Crossworld's creators. If they do not want to be linked with Crossroads, that portal still technically exists, but it will never be found in any Crossroads story.
Crossroads appears to have a sun, which sets and rises on a roughly twenty-four hour cycle, and a moon similar to that of most Earths. No one has ever been able to explain how this is possible given the geography. The sun rises earlier the farther one goes to the east, just as if Crossroads were a spherical planet. Attempts to send spacecraft up into the atmosphere reveal that air appears to extent infinitely upwards with no drop in pressure, and the temperature remains roughly the same. The sun and moon never appear to get any closer. At night there are stars in the sky, even though stars like those found in most Crossworlds would be impossible. Investigations into magical causes have so far been inconclusive.
Explorers have encountered seas and oceans, some of fresh water and some of salt. Weather patterns tend to also mimic those of a spherical planet. The terrain, animal life, and planet life is largely similar to that of most Earths, but there are many regions that are significant exceptions. Societies and technological levels vary wildly from area to area, usually depending on the nature of the Crossworlds portals in that area connect to. Magic, psionics, superpowers, high technology, and all other contradictory sets of physical laws all function at the same time.