Darkover is the focus of the Darkover series of science fiction novels and short stories by Marion Zimmer Bradley and others published since 1958. According to the novels, Darkover is the only human-habitable of seven planets orbiting a fictional red giant star called Cottman.
Like its neighbor, Darkover is a planet stuck in a permanent ice age. Only one small equatorial strip of its single smallish continent is warm enough to support limited agriculture, fishing, and livestock. But the planet's climate is harsh by any standard, with the warmest parts of the world snow-free for only a few weeks out of the year.
Similar in size to Earth, Darkover has a lower gravity due to its relative lack of metals; it also has a higher percentage of oxygen in the atmosphere. One Darkover year is roughly equal to 15 Earth months.
Darkover's four moons vary in size and color, two appear large from the surface of the planet. The largest is named Liriel, and appears to have a violet tint. The second largest, Kyrrdis, is described as "peacock blue." The third, sea-green hued Idriel, appears to be mid-range in size, while the fourth, Mormallor, is a very small white moon. It is thought that Mormallor may have been a passing asteroid that was captured by Darkover's gravity.
Viewing Darkover from space, the planet is dominated by polar icecaps that cover a majority of its surface. The sole continent, just a few degrees north of the equator, is linked to the northern icecap on the continental northern and eastern side where glaciers from The Wall Around the World mountain range abut the cap. To the south and west of that mountain range is Darkover's nominally temperate continental zone which borders the open water of the planet's ocean.
This part of the continent is dominated by forests of giant evergreen trees that grow in the mountain foothills to heights unimaginable on Earth due to the planet's lower gravity. These trees contain high amounts of flammable resins which are contribute to numerous forest fires during the warmer months. Further, southwest from the forests are Darkover's highlands, plains, salt marshes and arable river valleys. On the continent's far western side is another mountain range called "The Hellers" and a high elevation cold desert plateau called "The Dry Towns."
The native fauna of Darkover includes a number of species not found on Earth. Earth fauna that is adaptable to severe cold can also survive on Darkover.
Colorful scorpion-ants inhabit the warmer areas and are responsible for occasional deaths among the inhabitants. They are social insectoids similar to Earth ants in hive activity, but considerably larger and their sting is deadly poison.
Banshees are large, flightless, blind, carnivorous birds that live in the higher elevations and occasionally venture into the mountain passes to feed on rabbit-horns and the occasional unwitting inhabitant. Banshees terrify their prey with their blood-curdling screams. This has the effect of making the prey flee, and thus become visible to the banshee's infrared (body heat) sensing system. While they may be blind, they are very efficient hunters with this infrared sensing mechanism, although they can not sense unmoving prey. Banshees are at least half again as big as an Earth ostrich. They have a hooked beak for tearing meat and can disembowel their prey in one motion with the sharp talons on their muscular legs.
Rabbit-horns are a small herbivorous mammal similar to a horned rabbit. They are consumed by the inhabitants and other fauna as a source of meat.
The Chieri are later explained in The World Wreckers as the last, dying remnants of a space traveling species whose abilities have dwindled with their fertility and ambition as a species. Darkover is their home world, which they once left searching for means to halt their extinction, and to which they returned when they had no hope left.
Chieri and humans are very similar biologically and can interbreed, which led to the emergence of humans with great psychic gifts, the Comyn. It is possible that humans are a sub-species of Chieri, as they seem to have come first. However, in Star of Danger, the Chieri who aids Kennard Alton and Larry Montray, tells them that the Chieri share common ancestors with the Trailmen and the Kyrri, though not with the Terrans.
Perhaps the most significant feature of Darkovan society is the presence of Laran, the psychic powers of the Comyn, who are the ruling class of Darkover. Various arguments are presented to explain the high presence of psychic abilities in the human population of Darkover. One of the most significant is that the human colony described in the 'first' chronological book, Darkover Landfall, received the genetic material which carried Laran from the Chieri who fathered children with human women, and who bore children with human men. The original population of the colony also derived overwhelmingly from certain areas of north-west Europe (the Scottish highlands, Ireland and the Basque country) commonly linked in popular belief and tradition with a high level of supernatural abilities such as the second sight.
The other, equally significant argument is that the planet itself contributed to the realization of psychic abilities in its human population, primarily through the star flower or Kireseth. The "ghost winds", where Kireseth flowers bloom in unseasonably warm weather and then produce a vast amount of the psychotropic pollen which give the winds their name, are described in Darkover Landfall as the first human experiences with Darkovan pharmacopeia and its psychological effects.