The Korsinite League was a political faction of the Lost Tribe of Sith on Kesh in the period of turmoil around the 3,000 BBY. They believed that Yaru Korsin and his daughter Nida Korsin were living gods and they adored them, believing that the first Grand Lord came from beyond, that the Lost Tribe of Sith was the body of the leader and that those who would imperil the body deserved neither mercy nor life.
The Korsinite League was founded from a former slave a century before 3,000 BBY, taking Korsin as a title for himself, separate from the hierarchy of Lords. Emancipated, he patterned his life after those led by the first Grand Lord and his successor daughter; as he declared, any worthy could aspire to Korsin-ness, just as he had. His followers took it to heart—and, being Sith, decided they could just as easily adopt the title for themselves. Which they all did, over the movement founder’s complaints—and, eventually, his dead body.
At the 3,000 BBY there were hundreds of self-named Korsins of either sex running about, chanting mantras and declaring their empire of one to the crowd at large. To strike up a conversation with a Korsinite was to risk death by cognitive dissonance and for theological reasons their most hated enemies were the Sisters of Seelah.