Gantoris was a Jedi Knight who studied at Luke Skywalker's Jedi Academy on Yavin IV. However, Gantoris was a Jedi Knight who was claimed by forces of the Dark Side well before his time. Gantoris grew up on the failed colony world of Eol Sha, a harsh world stricken with lava pits and constantly harassed by earthquakes. A descendent of the original colonists, Gantoris was born with sensitivity to the Force, allowing him to survive in his harsh world. As a child, Gantoris and his clan were caught in the path of an oncoming avalanche. All of the adults were killed, while Gantoris remained unharmed; his sensitivity in the Force allowed him to escape death at the hands of Eol Sha's cruel environment.
As he grew older, Gantoris became more and more adept at predicting when earthquakes would occur, obviously an extension of his innate Force powers, and proved to be a valuable asset to preserving the safety of the people of Eol Sha. Because of his abilities, this led Gantoris to be elected leader of the descendents of the Eol Sha colonists. After the Empire was defeated, Luke Skywalker wanted to push forward his plans to reestablish the Jedi Order, and began searching the galaxy for Force-sensitive individuals that he might be able to train as Jedi Knights. Finding information about Eol Sha, Luke Skywalker traveled there to meet with Gantoris in hopes of convincing him to return to Yavin IV with him to study the Jedi way.
However, Gantoris received Luke with a cautious mind. For sometime prior to Luke's arrival, he was haunted by visions of a 'dark man' that would destroy him. In order to test Luke's motives, Gantoris put Luke to a small number of challenges. One of the required Luke to cross a lava pit and battle a lava dragon, a silicon based lifeform resembling a dragon that had adapted to live in the molten lava of Eol Sha. With successful completion of the tasks, Gantoris accepted Luke and his offer agreeing to return with him. However, he was concerned about the welfare of his people, and did not want to leave them behind. Working out a deal with his sister, Leia Organa-Solo, Luke arranged for the people of Eol Sha to be relocated to the much more welcoming environment of Dantooine.