Yoda was a wise, experienced, and powerful Grand Master of the Jedi of an unknown species and the oldest known prophet in existence (having lived at least 900 years), considered the wisest and most powerful Jedi Master within the "Star Wars" universe. He was knighted at age 100, and spent the next eight centuries mentoring several generations of Jedi, about 20,000 of which he took as Padawans. During this period, the green Jedi Master formed good relations with the Wookies of Kashyyyk on numerous occasions, such as when he saved their Terentatek. Following the Galactic Republic's transformation into the Galactic Empire, Yoda was one of the few Jedi survivors of Order 66, and spent the rest of his life on the swamp planet Dagobah. Hiding from the Empire, he trained Luke Skywalker in the Jedi arts, until dying of old age, though he returned as a Force spirit. In the sequel trilogy, Yoda appears both as a Force spirit, teaching an older and wiser Luke about failure, and as a disembodied voice alongside other past Jedi, empowering Rey to face a rejuvenated Emperor Palpatine.