As Sith Lords, Darth Vader and his master Emperor Palpatine clashed several times in the established Star Wars canon (with varying results).

The apprentice who kills Plagueis that story is referring to is meant to be Palpatine, Darth Sidious. But before Sidious, the idea appears to be that during his artificially extended life ...

During their duel, Maul warned Ahsoka that Darth Sidious was about to enact his plan to seize control of the universe, and that her master Anakin Skywalker was the Sith Lord’s chosen apprentice.

Reddit user GLOV3R put Ahsoka’s duel with Maul side-by-side with Mace Windu‘s duel with Darth ... apprentice. Her former master gives into temptation, rescues and swears fealty to Sidious ...