Obi-Wan appears as a Force ghost in many novels set after "Return of the Jedi". In "The Truce at Bakura", he appears to Luke to warn him about the threat presented by the Ssi-ruuk; in "The Lost City of the Jedi", he guides Luke to the titular city on Yavin IV; in "Heir to the Empire", meanwhile, he bids farewell to Luke, explaining that he must abandon his spiritual form to "move on" to a new, higher plane of consciousness. Before parting, Luke says that Obi-Wan was like a father to him, and Obi-Wan replies that he loved Luke like a son.