However, they soon received help from Jedi reinforcements from Ossus and the two forces launched a two front attack on the Naddists, meeting in the middle. No longer trapped, the Jedi and Beastrider forces launched an attack on Ommin's citadel in an attempt to rescue Arca. Oss fought alongside Jedi such as Nomi Sunrider, Dace Diath, and Qrrl Toq. They eventually made their way to Ommin's inner chambers and were able to defeat him, freeing Master Arca from his Dark Side prison. With the darkness finally extinguished in the walled city, Oss and the rest of the Jedi took to the business of entombing Freedon Nadd's remains on Dxun moon.

After the events of the Freedon Nadd Uprising, Oss and Jedi remained on Onderon to learn to ride the planet's great, winged beasts. During one such session, Jedi Master Arca called Oss and the Jedi to a meeting. He explained that a coup in the Empress Teta System-orchestrated by a group calling themselves the Krath, was somehow related to the recent Freedon Nadd Uprising, and that the use of Sith magic was evident. Arca explained that a task force would be sent to the Empress Teta System consisting of combined Jedi and Republic forces. Arca split the Jedi into three groups, each sent on different missions. Oss was part of the group sent to Ossus to report to the Jedi Masters there of the events they witnessed on Onderon. And so, as Nomi Sunrider and Ulic Qel-Droma left for the Empress Teta System, and Cay Qel-Droma and Tott Doneeta remained on Onderon, Oss Wilum, Dace Diath, Shoaneb Culu, and Qrrl Toq left for Ossus for a meeting with the Jedi Masters on planet.

After having arrived on Ossus, the galaxy was soon thrust deeper into conflict when the Krath openly declared war on the Jedi. Also, a young Jedi's fascination with Sith magic and alchemy threatened to bring about a resurgence of the Sith Empire. After having relayed the most recent information to the Jedi Masters on Ossus, a convocation of Jedi was called for on the planet of Deneba to discuss the growing evil. Oss, along with thousands of other Jedi left for the convocation that would take place at Mount Meru. At the convocation, Oss contributed his thoughts on the ancient Jedi prophecies that foretold of a war with the Dark Side. The peace of the convocation soon came to an end when a surprise attack by the Krath pitted thousands of battle droids against the Jedi forces.

During the ensuing battle, Oss fought alongside his fellow Jedi to defeat the droid army. After the battle, Jedi Knight Ulic Qel-Droma announced his plan to join the Krath in an attempt to destroy it from within. The Jedi, along with Oss Wilum, returned to Ossus to strategize over the war. On Ossus, Oss and fellow Jedi went to work testing out new StarSaber attack ships that might prove useful in battle against the Krath forces. Soon however, Jedi Knights Cay Qel-Droma and Nomi Sunrider brought news of Ulic's attempts to infiltrate the Krath. Both believed that Ulic was going to far in his attempt and was beginning to be seduced by the Krath's Dark Side ways.