Yun was a member of the Reborn Sith Order. After the Attack on the Jedi Temple, he and Sariss infiltrated the New Republic military. Tahiri Veila and Aren Lical attacked the two Sith and killed Sariss, but they captured Yun alive and interrogated him. Yun was the only member of the Reborn Sith Order who was left alive. He was kept prisoner in the praxeum on Yavin IV, and eventually turned to the light side.