Library of Ossus

Approximately 5,000 BBY, the scholarly Jedi Knight Odan-Urr founded a center of Jedi Learning on the planet Ossus where he was trained. From it's beginning, the Library of Ossus contained much knowledge and wisdom. Scrolls and books filled shelves, and many Jedi Holocrons were stored there. Among the artifacts was a Sith Holocron that Odan-Urr himself had recovered from a Sith warship in the aftermath of the Great Hyperspace War.

For over a millenium the Library of Ossus continued to grow, and soon many great Masters worked there, tending the shelves and teaching Jedi who wished to learn. One of these was the Neti Jedi Master Ood Bnar.

Approximately 4,000 BBY, the Library was visited by the Sith Lord Exar Kun, who seduced many young Jedi to the dark side. When he had gathered enough followers, he went to Master Odan-Urr and demanded that he turn over the Sith Holocron. When the ancient Jedi refused, Kun brutally slew him and took the artifact. Thus Odan-Urr died surrounded by the books he loved so much, even as his own teacher, Master Ooroo, had predicted.

Soon after, Kun's forces used an ancient Sith weapon to unleash a cataclysm that would wreck the surface of Ossus. As the Jedi scrambled to evacuate the scrolls and artifacts, the Sith came one last time. Ood Bnar, utilizing an ability unique to his species, buried an collection of ancient lightsabers and literally "planted" himself over them, becoming a tree-like being and binding his life force to the planet's, thus insuring that the Sith would not desecrate the ancient Jedi weapons. Soon, all the Jedi had evacuated As the shock wave hit Ossus, Master Bnar weathered to storm alone.

Millenia later, roughly a decade after the Battle of Yavin, Luke Skywalker and Kam Solusar traveled to Ossus to find the remains of the Great Library. There they discovered that the planet had become the home of a humanoid race called the Ysanna. Soon after, Imperial Executor Sedriss arrived with a small force, and after a battle (in which the Jedi were aided by the Ysanna) all but Sedriss had been defeated. Luke pushes Sedriss against a tree, only to find that it isn't a tree at all. It is Ood Bnar. Sensing the battle, the ancient Jedi intervenes, grabbing Sedriss with his limbs. As Sedriss tried to fight Bnar through the Force, Ood reached deep into the planet's life force and destroyed himself, taking Sedriss with him. Thus, Skywalker and Solusar were free to recover the lightsabers hidden under Ood, still working after all those millenia. Afterwords, Skywalker received permission from the tribal chief to take two Ysanna youths to train as Jedi.

Skywalker and Solusar later found the ruins of the Great Library, and found many secrets that helped them to rebuild the Jedi Order.