Systian

Syst, properly called the Systians or the Children of Syst, were a human-like race from the planet of Syst. They were a secretive race, hiding their faces and their true culture. They were renowned mercenaries, hired by many races. After the Sith claimed their planet, the Syst fought briefly for their new masters, but following the Jedi Wars, they rebelled against their Sith masters and freed Syst, proceeding to free their Stymphogian allies.

Advaros Greyn and the rebellion
After the Sith were weakened by their defeat in the Jedi Wars, the Syst master-assassin Adravos Greyn raised a rebellion on Syst to claim independence. Despite their higher numbers, the Sith garrison was still outmatched and outgunned, and Adravos lead a swift and deadly military coup. He later became the leader of the Systians, and aided the Stympogians in their bid for freedom.