Oss Wilum was a former Jedi and an antagonist in the Tales of the Jedi series.
Wilum was apprenticed to Jedi Masters Garnoo and Thon. During his time as a Jedi Knight, he aided fellow Jedi Ulic Qel-Droma in fighting the Naddists in the Sith War. Wilum was one of the few Jedi to be enlisted in Exar Kun's crusade against the Jedi Order and the Galactic Republic. He followed him to Ossus and Yavin 4 where Kun smashes a Sith holocron that influences Wilum to join him.
Exar Kun sent Wilum and Crado to kill Thon on Ambria. Wilum summoned two Hssiss with his new Sith powers but the two creatures were cut down by Thon. Thon captured his old apprentice and was able to redeem him.