Soon after on Cinnagar, Odan had a vision through the Force of the distant and pretty much unknown Sith Empire, gathering its forces for an attack on the Republic. Trusting in Odan's judgement, Memit Nadill backed Odan as he told Empress Teta of his vision, and the Empress resolved to travel to Coruscant with Odan and Memit to tell the Republic. On Coruscant however, as Empress Teta addressed the Galactic Senate and other Jedi who had come, the audience refused to believe the Sith posed a threat to the Republic, for many had thought the Sith long extinct, and they had fallen into the category of mythology. Undeterred, Empress Teta and her Jedi advisors set out to gather other forces.

Back on Cinnagar, Empress Teta went to work on reconstructing her fleet, which had taken damage from the recent Unification Wars. During the reconstruction, Odan was surprised to find that his Master, Ooroo, had joined him on Cinnagar. Ooroo believed that Odan was correct in his interpretation of his vision, and had come to help him prepare for the invasion. Once the invasion began, the rebels army, the very enemy Empress Teta fought against in the Unification Wars, pledged their alliegance to her, and Odan-Urr and Master Ooroo traveled to Kirrek to fight along side the rebels to defend the Republic. As a scholar, Odan found it difficult to thrust himself into battle, even when it appeared as if the Sith might win the Battle of Kirrek.

Realizing what he must do, Odan's teacher told him to find shelter and placed himself in the middle of the battlefield. Releasing the deadly gas that he required to live, Ooroo's last act as a Jedi was to sacrefice himself to wipe out the majority of the Sith forces. As Ooroo lay dying, Odan-Urr ran to his side to comfort him as he passed into the Force. However, before he did so, Ooroo made a prophecy that Odan would become a great Jedi, and live for many centuries before passing into the Force among his beloved books. With that, Odan grieved the loss of his master, and as more soldiers arrived, the Sith forces on Kirrek as well as elsewhere in the Republic were pushed back. Once the battle was over, Odan made his way onto an abandoned Sith warship. There he found his most prized possession, a Sith holocron. As he wandered the ship, he remembered his master's final words, and decided to build a learning center, a Jedi Library on the planet of Ossus.

Odan-Urr did as he planned and built a great Jedi Library on Ossus where Jedi came to teach and learn for the next thousand years. Odan-Urr also served the Jedi over the next millenium. Odan-Urr became known as the 'Keeper of Antiquities,' and spent much of his time meditating and thinking on what it meant to be a Jedi. He authored a famous commentary on the interpretation of the Jedi Code which held true for centuries and was taught to all young Jedi students. Six hundred years before the great Sith War, Odan-Urr became the spokesman for the Jedi assemblies and retained that position for six centuries, up to the time of the Jedi convocation on Deneba.