Ood eventually became the understudy of Head Librarian Odan-Urr at the Great Jedi Library on Ossus, and after his friend's death at the hands of Exar Kun during the Great Sith War in 4000 BBY, Ood took over his role as Head Librarian. However, his reign would not last long. He was among the Jedi who discovered that they would have little time to evacuate before Ossus was destroyed by a Sith-created supernova in the nearby Cron Cluster. While the other Jedi hurried to save as much as they could, Ood went to his bundle of ancient lightsabers, hoping they would survive the shockwave heading for the planet. However, he was interrupted by Exar Kun, who had come to Ossus to scavenge any artifacts left behind. Knowing he could not defeat the Dark Lord of the Sith, Ood transformed into a giant and