InStar Wars: Revenge of the Sith, Emperor Palpatine tells young Anakin Skywalker about a Sith lord named Darth Plagueis.
"Darth Plagueis was a Dark Lord of the Sith so powerful and so wise he could use the Force to influence the midichlorians to create life,"Palpatine explains. "He had such a knowledge of the dark side that he could even keep the ones he cared about from dying ... The only thing he was afraid of was losing his power. And fortunately, he taught his apprentice everything he knew, then his apprentice killed him in his sleep."
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