Sith (species)

The Sith populate the planet of Tyriun, however, their past places them on the planet of Ziost, where originally the Sith had been enslaved. Their eyes are varying in color, although many of the Force Users have distinguishly black or white eyes, which make it easy to tell who wields the Force amongst the Sith.

The Sith have long been associated with the Dark Side, since it was originally the Dark Jedi that the Sith bred with who turned the Sith into what they are today...

History
In the past, the Sith had red skin and tentacle beards. They were generally weak minded, although several were very intelligent. This made things very unorganized, and the Sith were easily conquered when the Force Wielding Dark Jedi came to their planet, and ended up enslaving them.

Eventually, the Sith bred with their Dark Jedi captives, and through this blending, the Humans and Sith became nearly one and the same, and the Sith gained their characteristic blue and pink skin throughout this process. Many of this new breed of Sith were Force Sensitive, due to the fact that the people who came before them were Dark Jedi.

The planet of Tyriun is mostly barren, and as such, the Sith, working with the Humans as their masters, have constructed vast temples to the Force on the planet, each which can house the Sith Masters and Human peasants, as well as which have small, underground areas for growing food and harvesting water from streams.

The Sith lead a complex life there. Born into a caste, a Sith's life is predetermined. There is a royal family that has been determined for years by power between the siblings of the family, or outside power for that matter, and there is a complex Bishop system which allows the Sith to worship the Force in manners of Priests and Religious exploits.

Since the planet was born entirely through the Force, it is not unlikely that is the reason why such a Force Sensitive species as the Sith inhabit it. The humans, though, were most likely chosen due to their intelligence and belief in something above them, and as such Tyriun is a great planet for the Sith to call their home.