Callista Ming

Callista is a Jedi Knight from the time of the Old Republic. She discovered a well-hidden secret Imperial installation (a sort of proto-Death Star, though with nowhere near the firepower) and attempted to sabotage or destroy it; when she failed and died, she used her talents in the Force to essentially 'haunt' the station's central computer. She remained there for thirty years, until Jedi Master Luke Skywalker and several other New Republic Jedi discovered the station and assisted her in destroying it. During the process, the two fell in love, and just prior to the station's destruction, Callista traded bodies with one of the other Jedi (a female). Unfortunately the process cut her off from the Force. Later experiments, though, found her still in touch with the Dark Side. Eventually she left on a quest to find a compromise to her powers, and the two are considered distinctly separated (especially in light of Skywalker's marriage to Mara Jade).