World crystal
A world crystal is a kind of élan crystal common on Varra, which encloses an entire pocket plane within it. A pocket plane within a world crystal is called a crystal world. World crystals are found all over the land surface of Varra, and while they may be more common in some places than others there is no large area of the world entirely free of them. World crystals even exist within the deathfields, though those there may be less accessible and less frequently visited, to such extent that many of the crystal worlds there may not have had contact with the main world of Varra in centuries, if ever. The same is true of the Smeltery, where apparently world crystals continue to exist beneath the ubiquitous magma. World crystals may even be as common in the depths of Varra's oceans as they are on land, though the evidence for this is uncertain; most Varrans have enough to deal with the bonelords and Thamarand that they don't have time for idle exploration.
While world crystals occur naturally partially embedded in the surrounding stone, nothing prevents the stone from being chipped away and the crystal from being removed from its resting place. World crystals are large and heavy enough, however, that even detached from the stone they are still hardly portable.
Description
A world crystal is largely indistinguishable from any other élan crystal, though they tend on the whole to be somewhat larger. Like many élan crystals, they generally take the shape of pyramid-capped prisms, with their cross sections bearing anywhere from three to nine edges. World crystals may come in virtually any color, and though many scholars suspect some connection between the crystal's color and its contents, no such relation has been definitively proven. Though world crystals may grow as large as four meters in length and girth, the median length is about 1.6 meters, and world crystals have been found as short as thirty centimeters.
In the case of most world crystals, nothing about the world within is visible from the exterior. Short of divination, only by entering the crystal (or by contact with something that has) can an investigator discover anything about its contents. A few crystals are exceptions to this rule, however, with hazy shadows across their surface mimicking some of the features within.
Entering and exiting
A person or object does not enter a world crystal by merely brushing up against it, or walking into it. Entering a world crystal requires the exertion of a pressure on the crystal's surface of about 31,000 Newtons (on average, though slight variation exists between crystals). The object exerting the pressure will then pass through the surface of the crystal into the world within. Once the surface is breached, continuing to exert pressure is not necessary; an object cannot become "stuck" partway into the surface, and in fact can readily bring with it other objects firmly attached to or gripped by it. The necessary pressure is one the average human can easily provide by pressing firmly with a palm, but much larger than will be produced by casual contact. As a result, humans and comparable life forms can enter world crystals relatively easily by intentionally pressing on them (bringing with them anything they are wearing or carrying), but are unlikely to accidentally enter a world crystal by merely leaning on it. (Accidental entrances by people falling against world crystals and contacting them first with an elbow or other body part with a small surface area have, however, occurred, albeit relatively infrequently.) If the part of the crystal world that an object would enter is occupied by a solid object, entry is impeded unless the force exerted is sufficient to push the object out of the way. A object does not have to be smaller than the crystal's face to enter it; indeed, world crystals can admit objects of at least five times their linear dimensions.
The orientation of a crystal world—with respect to gravity and other intrinsic forces—does not necessary match that of Varra outside it. Depending on the relative orientations, a person entering a crystal world may there find himself suddenly on his side, or upside-down. However, the gravitational field of a crystal world almost always runs parallel to the crystal's axis—that is, along the length of the prism, from one pyramidal cap to the other—and most (though not all) crystals do occur with their fields more or less aligned with that of their Varran environs. While a crystal lying horizontal on the ground may present a mystery as to which end is "up", therefore, most of the time when encountering a world crystal standing vertical one can be fairly confident that one can push one's way into it and remain on one's feet inside.
Where one ends up in the crystal world on entering the crystal generally depends on the part of the surface where one entered. While the correspondence between points on the inside boundary of the crystal world and those on the surface of the crystal is homeomorphic, it does not preserve relative distance. Small areas of the interior boundary may correspond to large areas of the external surface; such areas, when well known, are sometimes known as wickets. It is here that most visitors to the world crystal are likely to arrive, unless they are very familiar with the world crystal and its workings and specifically go out of their way to avoid the wickets. The converse is also true: large parts of the interior boundary may map to relatively small areas of the external surface. In particular, for most world crystals a majority of the exterior surface corresponds to a band within a meter or so of the land surface of the crystal world; only by entering near a tip of the crystal can one arrive within the crystal world high above or below the surface. In a way, this is fortunate, since it minimizes the chances that someone will enter a crystal world far above the land surface only to plummet immediately to his death. For the most part, one is safe from this fate as long as one doesn't try entering the crystal near its tip—though the rare crystal worlds in which the gravitational field does not run along the crystal's axis, and in which it is not the tip of the pyramidal cap that corresponds to the boundary area high above the land surface, are therefore especially dangerous.
All known crystal worlds are finite in area and bounded, and leaving the crystal world and returning to Varra is simply a matter of moving past the boundaries. The boundary of the crystal world does offer some resistance to passage through, so the exertion of pressure is required to leave the crystal just as it is to enter it, but the pressure needed is only about half the pressure to enter, so leaving crystal worlds is usually easier than entering them.
Worlds
The crystal worlds within the crystals vary widely in their sizes and characteristics. While most of them are terrestrial, a few crystals hold more exotic worlds, often to the misfortune of those who stumble into them. Many crystal worlds are home to unique life forms found nowhere else, some of which have since found their ways out of their crystal cradles to colonize other crystal worlds and the surface of Varra. Some crystal worlds even sport unique arcana and physical laws. Indeed, some æalogists hold that some, or perhaps all, crystal worlds technically compose their own small cosmoi.
While the cross sections of most of the crystal worlds are roughly circular, they come in a variety of different sizes. No known crystal worlds are as expansive as Varra itself, but some approach the same order of magnitude. The smallest crystal worlds, meanwhile, are barely a few kilometers across. The median diameter of the crystal worlds seems to be roughly four hundred kilometers, but with much variation on both sides—and while any individual crystal world may be significantly smaller than Varra, the total area of all the crystal worlds combined almost certainly exceed Varra's.
Creation and destruction
While most scholars believe that the world crystals share the same origins as other élan crystals (whatever those origins may be), others see them as unusual enough to warrant conclusions about a separate source, though none have proffered a good explanation as to what that source may be, Some of the crystal worlds have histories going back hundreds of thousands of years, but this doesn't necessarily mean that the world crystals themselves are really that old; it could be, for instance, that the crystal worlds were somehow imported from elsewhere, or it could be a case of parogony. There is some evidence that new world crystals are still being formed somehow, though the difficulty of carrying out detailed studies on Varra's benighted surface makes this a difficult proposition to prove. Not a few mages have attempted to create their own world crystals, though none with notable success.
Even more so than other élan crystals, world crystals are very difficult to damage or destroy, especially since large forces, rather than breaking the crystal, instead cause the objects exerting the forces to pass inside them. Only one recorded case exists of a world crystal actually having been split in two, by means that remain unclear. While the crystal world within, Syrana, remained in one piece, a strange sort of field appeared in it in a position corresponding to the fracture. As for the crystal itself, the broken surfaces looked greyer and darker than what had been the crystal's exterior, but no longer led to Syrana—where exactly they did lead is unknown, since no one and nothing that entered has returned.
While it may be nearly impossible to break a world crystal with physical force, they are somewhat more susceptible to other forms of harm, such as intense heat or chemical dissolution. Even against these they remain extremely resistant—world crystals can withstand temperatures that would melt most rocks—but not entirely impermeable. When a world crystal is partially destroyed, the crystal world within is intact but not unchanged, though too few examples exist of this occurring to extrapolate general conclusions as to usual effects. Whatever happens to the crystal world's interior, it does seem that the boundary corresponding to the annihilated part of the crystal is still permeable but leads no longer to Varra, but to some strange and unhealthy alien plane. (Whether it is the same strange and unhealthy alien plane for all damaged crystals is uncertain.) The bonelord Yjiau is thought to have completely destroyed at least three world crystals by these means, but powerful divinations have shown that at least one of the crystal worlds still exists—though assumably cut off from Varra—so it seems that somehow, at least under some circumstances, crystal worlds can survive even the destruction of their crystals.