Uuari
The uuari (pronounced /uːˈwɑri/) is a life form of Diddu that seems to be composed entirely of light. As such, it can move freely through any transparent objects and materials, and somewhat more slowly through translucent ones, though any materials that are fully opaque are impenetrable to it. They travel through clear water as easily as through air, and are almost as likely to be found underwater as over the land, and in the skies far above the world as near its surface. Uuari are unusual among Didduan life forms in that they are apparently unaffected by the world's mestral transformations; the uuari remains active and unchanged regardless of the mester.
Description
The uuari appears like a serpentine smear of white light, undulating as it travels through the air or other photically permeable media. It has a scalloped or jagged outline, somewhat as if slightly brighter light were shining out from some spots than others. While to most other beings, any two uuari look identical (with the possible exception of some injured or anomalous specimens), the uuari seem to have no trouble telling each other apart, and there are some humans and others who claim to have learned how to distinguish between them, based on slight differences of shape and pattern of luminosity.
The general shape of the uuari seems to be that of a flat ribbon with rounded ends, though its poorly defined outline makes this somewhat questionable. A typical uuari is about 60 centimeters long, 15 centimeters wide, and perhaps a few millimeters thick, though this last dimension is particularly hard to judge. Much larger and much smaller specimens have been encountered, though the relative proportions of their dimensions remain fairly constant.
Biology
The biology of the uuari is very poorly understood. It seems to have no tangible form, but it's not completely clear just what it is made of. Certainly nothing is known of the uuari's anatomy; the beings seem to evaporate upon death, and no one is known to have been in any position to closely examine a living specimen. They do seem to have some susceptibility to physical damage; any opaque object can deliver a damaging blow to them, and, with sufficient force, potentially kill them—although anything short of complete bisection seems to be almost immediately healed.
Behavior
Uuari for the most part seem inquisitive but aloof. They may approach a human or other sophont and flit about him in apparent curiosity, but make no attempt to communicate, and fly away rapidly if disturbed. (An uuari can move at a speed of some seventeen meters per second, far too fast for a human on foot to catch up, though not faster than a fleet horse.) Because of their uncommunicative nature and alien behavior, many people dismiss the uuari as an unintelligent beast. This, however, is an error; uuari in fact compose an ellogous race, just one that seems to want little to do with man. Moreover, it is possible to communicate with them, though it usually requires magic—uuari communicate with each other through subtle variations in their light patterns which are nearly impossible for humans to interpret, and, conversely, uuari seem to have no sense of hearing and therefore no way to understand human speech.
The uuari's diet comprises certain gases not commonly found in the air as a whole but only near certain places, including active volcanoes and some swamps. However, they need to eat fairly infrequently, and may range far from any area where these foods are available. If hard pressed, they seem to be able to extract their needed nutrients from some solids, but this is a time-consuming and difficult process for them, and one they generally undertake only if absolutely necessary.
Reproduction
Often taking place high in the atmosphere, uuari reproduction is rarely witnessed by humans. Still, a few reports of it do exist. Reproduction requires three uuari, no more and no fewer, which begin circling around each other and then moving in more complex patterns, building up speed until they visually merge together into a spherical blur that steadily brightens. After ten to twenty minutes of this, they gradually slow down, but when they finally become separately distinguishable again their number has increased, from three uuari to anywhere between six and ten.
It isn't clear whether uuari have multiple genders, or whether this procedure can be performed by any three uuari.
Behavior
The uuari seem to be mostly solitary entities, and more than one uuari have rarely been seen together apart from during the reproductive process (and even that has been rarely seen). Some have suggested that the uuari do have communities high in the sky above Diddu, but there is little or no concrete evidence for this. Some of them wander the world apparently at random, others seem to confine themselves to relatively small areas, only leaving occasionally to find sustenance. In any case, for the most part, uuari seem to have little interaction with other beings of their own kind or of others.
On rare occasions, some people have managed to forge, if not exactly friendships then at least some sort of acquaintanceships, with individual uuari. Exactly how they accomplished this feat and persuaded the uuari to interact with them is uncertain, but they have found the beings very useful to keep track of what goes on during the mesters when humans aren't active.