planet Korriban
Read more at the SW:TOR official site:HOMEWORLD OF THE SITH
The earliest Sith lived on the red, dusty planet of Korriban, determined to grow strong despite the inhospitable climate. Their success culminated in a bold civilization, made stronger when dark Force-users arrived and interbred after being driven out of the early Jedi Order. This ancient Sith civilization eventually became a superpower and challenged the Republic during the Great Hyperspace war. Their defeat drove a handful of survivors into deep space where they regrouped and rebuilt, determined to return.
Star Wars: The Old Republic | HOLONET Planets | Korriban