"Commonly referred to as Baron Harkonnen, his title is officially Siridar (planetary governor) Baron. Vladimir Harkonnen is the direct-line male descendant of the Bashar Abulurd Harkonnen who was banished for cowardice after the Battle of Corrin. The return of House Harkonnen to power generally is ascribed to adroit manipulation of the whale fur market and later consolidation with melange wealth from Arrakis. The Siridar-Baron died on Arrakis during the Revolt. Title passed briefly to the na-Baron, Feyd-Rautha Harkonnen." - Appendix IV of Dune
Baron Vladimir Harkonnen is probably the main antagonist of the first Dune book, being the leader of the evil House Harkonnen. He appears in all the books of the Prelude to Dune, as well as the first Dune book, in which he dies at the hands of a young Alia Atreides wielding the Gom Jabbar. He also later returns to possess Alia in Children of Dune. He is known for his sadistic nature, extreme obesity, and great love of young boys. According to the Prelude books he was, at first, a good-looking, muscular man. However, when trying to rape Reverend Mother Gaius Helen Mohiam, he was infected by a disease which caused him to become so fat that he eventually had to be carried around by a suspensor belt at all times to move.
When he was killed by Alia, House Harkonnen passed to his na-Baron, Feyd-Rautha Harkonnon. He challenged Paul Atreides to a duel, which Paul won. After Paul defeated Feyd, House Harkonnen passed to the next living heir, the Lady Jessica, who declined the title. Paul then ruled that House Harkonnen passed to himself as the last living heir, and became subsumed into the throne.
Approximately 15244 A.G, Vladimir was resurrected as a ghola by the Lost Tleilaxu Uxtal at the bidding of the new generation of Face Dancers. He was decanted on Tleilax, but later moved by Khrone to Caladan to be raised by the Face Dancers. He was eventually given charge of a ghola of Paul Atreides, being told by Khrone that the Atreides ghola would be very important to their plans soon.