Have you ever heard the tragedy of Darth Plagueis the Wise? I thought not. It's not a story the Jedi would tell you. It's a Sith legend. Darth Plagueis the Wise was a Dark Lord of the Sith, so powerful and so wise he could use the Force to influence the midichlorians to create life. He had such a knowledge of the Dark Side, he could even stop the ones he cared about from dying. The Dark Side of the Force is a pathway to many abilities some consider to be unnatural. He became so powerful... the only thing he was afraid of was losing his power, which eventually, of course, he did. Unfortunately, he taught his apprentice everything he knew, and his apprentice killed him in his sleep. Plagueis never saw it coming. It's ironic he could save others from dying, but not himself.
— Star Wars: Episode III - Revenge of the Sith
by George Lucas