Throughout the novel, 'native' myths and legends are interspersed, illuminating the beliefs and psychology of the Gethenians and Estraven's unspoken past. One story discusses the place inside the storm, a quiet haven within a blizzard. Another discusses the roots of the Yomeshta cult (the 'official', organised religion of Orgoreyn, much younger than, but ultimately derived from, the immensely ancient Handdara philosophy/religion). One is an ancient Orgota creation myth. A fourth discusses what a traitor is (the story concerns an ancestor of Estraven).
The inhabitants of Gethen are sequentially hermaphroditic humans; for twenty-four days (somer) of each twenty-six day lunar cycle, they are sexually latent androgynes; and for the remaining two days (kemmer), they are male or female, as determined by pheromonal negotiation with an interested sex partner. Thus each individual can both sire and bear children. Throughout the novel Gethenians are described as 'he,' whatever their role in kemmer. This was also the case in Le Guin's pre-Left hand of Darkness short story "Winter's King" when it was originally published; but in the interests of equity, when it was republished it in the collection The Wind's Twelve Quarters, it was rewritten so that all Gethenians are referred to as 'she'.
Physically, the Gethenians are mostly brown-skinned, but within a wide compass of variations. Most do not have facial hair, but their breasts are only a little larger than those of human males. The Envoy from Earth is darker-skinned (and taller) than most Gethenians, but can pass for a native while wearing indigenous clothing: the same was true of earlier observers who hid their identity.
It is suggested that the Gethenians were genetically engineered for hermaphroditism long ago by the original Hainish civilization, who planted colonies on many worlds, including Earth. That culture collapsed, and the Ekumen has only limited knowledge of the actions and motivations of their predecessors and their former colonies. The Gethenians might have been engineered to maximize reproductive success on the harsh glaciated world of Gethen, in an attempt to eliminate war, or as a social experiment.
Le Guin developed this idea out of a desire to explore what remained basic to human nature when biological sex was no longer a factor. The Left Hand of Darkness is a significant milestone in the increasing sophistication of the treatment of sex in science fiction that developed in the late 1960s and 1970s.
Shifgrethor is a fictional concept in Le Guin's Hainish Cycle universe, first introduced in 'The Left Hand of Darkness'. In the first mention, Le Guin's character Genly Ai thinks to himself "...shifgrethor--prestige, face, place, the pride-relationship, the untranslatable and all-important principle of social authority in Karhide and all civilizations of Gethen." It derives from an old Gethenian word for shadow. People of Karhide, being portrayed as the darker nation or Yin (in the idea of Chinese Tao), use this concept as a way of showing respect, whereas in Orgoreyn, which is portrayed as the lighter nation or Yang, they do not use shifgrethor but instead act in a direct manner with a falseness beneath it.
According to University of West Georgia Professor Carrie B. McWhorter, shifgrethor can be defined simply as "a sense of honor and respect that provides the Gethenians with a way to save face in a time of crisis."