This video closely follows the opening of the Darth Plagueis novel, which I listened to as an audiobook. Darth Plagueis was the master of Emperor Palpatine. In the movie Revenge of the Sith, Palpatine talks about killing Plagueis in his sleep.
I also listened to the Darth Bane trilogy, whose events took place long before this novel. Bane established the Sith "Rule of Two," which means that there should always be just one master and one apprentice. He eliminated the other Sith and took on a new apprentice. His unusual goal was that the apprentice should eventually kill and replace the master, or die trying.
Some of the mythology of Star Wars is explored and expanded upon in surprising ways in the different animated series.
