Darth Vader
Darth Vader is the principal villian of George Lucas's Star wars saga. The character was ranked as the third greatest villian in american film history by the American Film Insitute. With his "skull/samurai" helmet and imposing appearence, the character has become synonomous with dictatorial rule.
Original Trilogy
In episodes IV, V, and VI, Vader serves the Emperor Palpatine. He is responsible for the building of both Death Stars. At the end of Episode VI, his dying act is turning from the Dark Side, with the help of his son, Luke Skywalker.
Prequel Trilogy
In the prequel trilogy, Vader starts as an innocent young child of about eight (Anakin Skywalker). As he grows, he begins to be seduced by the Dark Side of the Force. When he has a vision that his mother is being tortured, and later when he sees her die, he kills an entire camp of Tusken Raiders. Later, when he has a vision about his wife, Padme, dying in childbirth, he turns to the Dark Side to try to save her. Ironically, his Force choke (Episode III) ends up being part of what killed her.