Vodo-Siosk Baas was a venerable male Krevaaki Jedi Master who served the Jedi Order with distinction before and during the Old Sith Wars. A warrior, historian and expert lightsaber crafter, Baas' life was devoted to the training of Jedi Knights to combat agents of the dark side of the Force. A respected member of the Jedi Order's Dantooine Enclave Council, Baas's time was divided between the Jedi facility on the world of Ossus and his academy for exceptional apprentices on the planet Dantooine. Although several of his students achieved fame for their efforts against the Sith, it was while under Baas's tutelage that a young Human named Exar Kun developed a fanatical desire for knowledge forbidden by the Jedi and abandoned his Master's wisdom in search thereof.
By 3,997 BBY, the influence of Sith magic had resurfaced and rapidly spread across the galaxy, with the Krath cult being the focal point and basing themselves in the Empress Teta system. Master Baas answered the summons of all Jedi to convene on the planet Deneba and discuss strategies against the new Sith, but while en route he felt through the Force the despair of his errant apprentice's fall to the dark side and became even more concerned with the future safety of the galaxy. The Deneba Jedi convocation fell under attack by the Krath, an attack that spurred Jedi Knight Ulic Qel-Droma into undertaking an infiltration mission of the Krath cult. Baas was among several Masters in meditation on Ossus who foresaw Qel-Droma's inevitable fall to the dark side, which culminated in his apprenticeship to the Dark Jedi Exar Kun, who had since become the Dark Lord of the Sith and had begun preparations for the restoration of a Sith Golden Age to the galaxy.
With the leadership of the Sith Brotherhood committed to war against the Galactic Republic, Vodo-Siosk Baas represented the Masters of the Order on a diplomatic venture to the Galactic Senate on Coruscant with a request for permission to handle what the Jedi considered to be an internal affair. He and his accompanying team of Jedi Knights subsequently participated in successfully defending the galactic capital from an combined invasion force of Krath and Mandalorians, led personally by Ulic Qel-Droma. With Qel-Droma's forces routed by the Republic and Qel-Droma himself captured, Baas returned to Dantooine for a time, contemplating what he could do in advance of the return of the Sith.
Baas became more determined than ever to prevent Kun's campaign of galactic tyranny from overtaking the Republic and he returned to Coruscant to meet his former apprentice before a full session of the Galactic Senate, taking place in the Grand Convocation Chamber of the Senate Hall. Kun himself met his former master in the Grand Convocation Chamber, where Bass made a final demand for Kun's renunciation of his chosen Sith path. Kun not only refused his Master's offer, but forced Baas into a duel with him, where the ancient Master was overmatched by both the Dark Lord's power and his lightsaber's concealed second blade. With his own demise at hand, Baas promised to one day return and vanquish Kun, whose killing blow then committed the Krevaaki to the Force.