The Sith, known alternatively as Red Sith or Sith Purebloods, were a species of red-skinned Humanoids that originated on the world of Korriban, before eventually resettling on the ice-world of Ziost. Also distinct for their bone spurs, facial tentacles, and genetic predispositions toward both left-handedness and the dark side of the Force, the Sith species coalesced into an empire ruled first by kings and later by Dark Lords. After the arrival of the Human Exiles on Korriban in 5900 BRR, interbreeding and genetic manipulation altered the Sith species; over the course of several generations the original species became a hybrid race of Sith and Human heritage. Original Sith blood became a symbol of pride among the Sith, with the term "Sith pureblood" referring to Sith who had a higher than average concentration of Sith blood.
Despite a society dominated by barbarism and infighting, Sith civilization culminated in a Golden Age, after which the species was all but scattered across the galaxy. An eponymous dark side tradition took the species' name, one that, despite numerous manifestations over time, maintained foundations borne of the customs, science and magic practiced by the ancient Sith species.
The Sith were a proud and violent species of humanoids that evolved on Korriban, a planet within the Horuset system in an isolated Outer Rim region called the Stygian Caldera. Sith had a larger than average number of individuals with potential to use the Force in their species, so high in fact that the entire species was considered strongly Force-sensitive. The abundant Force-sensitivity resulted from a symbiotic relationship with the dark side of the Force, where they—like the other few creatures that inhabited the planet—derived sustenance directly from the dark side of the Force, and empowered it in turn.
Adult Sith characteristically had skin of a crimson-hue, although infants of the species appeared a lighter shade of red. However, even though typically a dark red, some members of the species retained more pink shades of skin tone in adulthood. Sith had sharp, fierce predatory profiles and features all over their bodies, including bone spurs protruding from under their skin at various locations like the elbows. Their faces displayed a notable pair of cheek tendrils that hung down from their high cheekbones. Sith also had cranial horns, pointed teeth, simian mouths below their small noses, and glowing yellow eyes covered by cartilaginous eyebrow–stalks. In addition, some Sith had long bony chins, while others did not show this trait and instead possessed less prominent chins that receded from their mouth. Most Sith had three clawed digits on each hand, and three on each foot; two forward facing and one backward facing. However, some Sith had five digits on their hands and feet. The Sith were commonly left handed too.
The cheek tendrils on the jowls of Sith that descended from their cheekbones displayed different expressions amongst their species through twitching and other movements. For example, slight curling of the tendrils showed that the particular Sith was of a rejuvenated attitude, while stroking of the right tendril was an expression of thoughtfulness. Also, quivering of the tendrils could show signs of anger, as well as a questioning expression when coupled with raising of the eyebrow–stalks. The Sith—specifically the Massassi subspecies—also had very keen senses relative to those of Humans, particularly their hearing, despite their small ears.
After their arrival in Sith space after the Hundred-Year Darkness, Human Dark Jedi began to interbreed with the Sith. For nearly two thousand years, superstition, loyalty and sympathy were bred out as the two groups interbred, and qualities such as cunning, ambition and affinity to the Force were favored, which shaped Sith society over the centuries. In the Sith Empire, as time progressed pure-blooded Sith were steadily bred out, resulting in only a few pure-blooded Sith left in the Sith Empire by the time of the Great Hyperspace War. Long after, the true species in the Empire were believed to have gone extinct due to the interbreeding process.
Golden Age of the Sith (first appearance)