After Major John Sheppard's arrival to Atlantis, he accidentally woke up the Wraith Queen, who guarded the City. But Galadriel, who is an Ancient, asked for his help to free and to drive home the City, back to Earth. She showed him what could have happened if he stayed and didn't go home, the Queen would defeat him too. Finally he successfully fulfilled his promise to Galadriel by killing the Queen and driving Atlantis back to home. Therefore Galadriel finally could join to the other ancients.