Darth Nihl's Sith Empire was founded by Dark Lord of the Sith, Darth Nihl and his followers of the One Sith, as a dark side organization in direct opposition to the Galactic Federation of Free Alliances, the Fel Empire, and the New Jedi Order.
Following the defeat of Darth Krayt, and subsequently the One Sith or New Sith Order, Darth Nihl immediately ordered the extermination of Darth Krayt's Sith troopers. Without Krayt's power and influence to keep them in check, the Sith troopers swiftly descended into madness and began targeting everyone at random, including members of the One Sith. With the war lost and their enemies victorious, Nihl commanded all of the surviving Sith to retreat from key worlds, such as Coruscant and Korriban to escape capture or death. As the newly-formed Galactic Federation Triumvirate asserted its dominance over the entire known galaxy, the One Sith remained in hiding as per Nihl's orders, ironically finding themselves in the same position that the Jedi endured for several years—hunted and on the run. With their empire destroyed and their capabilities severely weakened, Nihl instructed his Sith followers to infiltrate every planetarygovernment in the galaxy, the Sith would continue to wage a war for galactic dominance through stealth, patience, cunning and secrecy.