In Episode VI, during their conversation before meeting the Emperor, Luke asks Vader to give up on the Emperor and join him instead, at which Vader replies: "You don't know the power of the Dark Side, I must obey my master". What does this mean? Is Vader somehow afraid of the Emperor? P.S. Please do not say it was a lie, a deceptive trick to get Luke to join the Dark Side, because clearly it has nothing to do with that. Answer We see in EU (E.g. in the Darth Maul novel) Sith training that rigid discipline and obedience is strongly enforced, with harsh punishments. The Emperor, as a more powerful Sith Master compared to Vader, can punish and hurt him (and has done so, e.g. cutting off his hand for losing Death Star 1 as told by Mara Jade). In addition, Vader is still a Dark Side aficionado, and needs the Dark Side to be able to hope to live at some point outside his life support suit. So, he needs the Emperor. So, yes, he must obey his master, both by his training; an