Emperor Palpatine and Darth Vader both seek Luke as their apprentice in the original Star Wars trilogy, but each of the two Sith Lords keeps other potential apprentices as backup options. The Sith Order is known for its Rule of Two, which limits the number of Dark Lords to just two at a time and ensures that only the deadliest Sith can keep their title. Given Luke’s sheer aptitude in the Force, it’s no surprise that Palpatine and Vader wanted to make him their Sith apprentice, but the two Dark Lords, especially Palpatine, barely let their plans depend on just one potential Sith apprentice.
The Sith Rule of Two was created by Darth Bane a millennium before the events of the Star Wars prequel trilogy. The doctrine served multiple purposes, reducing the tendency of the Dark Lords to betray each other and using it to keep order as strong as possible. The Sith Master is constantly looking for a new and better apprentice as they attempt to overthrow their master and get an apprentice of their own. As shown in both canon and Legends Star Wars timelines, Vader and Palpatine continued to adhere to the Rule of Two even after the Sith took control of the galaxy and nearly destroyed their old enemies, the Jedi Knights.
In both Star Wars continuities, there are many more than two dark side users within the Galactic Empire, but only Palpatine and Darth Vader are true Sith Lords. Upon his discovery, Luke Skywalker became a staple of both Dark Lords’ respective gambits for treason, but Palpatine, once the schemer, had potential replacements for Vader well before he even considered Luke. In Legends, the most prominent of these potential Sith Lords Mara are Jade, Jerec, and Cronal, while in canon Palpatine has a seemingly limitless supply of dark sideways beach casts hidden in his secret lab on Exegol. While not as ambitious as his master, Darth Vader also has potential Sith apprentices in the form of Lumiya, Flint, and Kharys.
Who else considered Palpatine replacing Darth Vader in Star Wars?
Aside from Luke Skywalker, Emperor Palpatine’s most obvious potential replacements for Darth Vader in canon are his cloned Sith Eternal guards. Debuted in Marvel’s Star Wars: Darth Vader comic series, they are described as such by Palpatine when Darth Vader discovers his master’s secret facility on Exegol and battles a group of the beach-cast warriors. Although Vader slaughters them, Palpatine’s resources allow him to grow more easily. In addition to the Sith Eternal guards, the Empire also uses dark-side trained Jedi fighters known as Inquisitors. These Imperial Inquisitors are all former Jedi and while they are by all means Sith by name, Palpatine and Vader make sure that their power is limited, reducing their potential threat to the two Dark Lords, but reducing their chances of becoming a real Sith. become extremely unlikely.
In canon, Darth Vader is particularly lacking in insidious ambition as a Sith Lord until the discovery of his son, Luke. Canon Star Wars comics have Palpatine notice this, making it highly unlikely that Darth Vader has any other potential Sith apprentices. While Darth Vader is undeniably Emperor Palpatine’s most powerful apprentice, his resignation from Sith Lordship and his ultimate lack of usefulness to the Empire give Palpatine more motivation to replace him than just following the Sith tradition. While the Legends-era Vader is one of the most effective leaders of the Imperial Army, the Canon Darth Vader, as emphasized by Cassio Tagge, is more of a figurehead for the Empire than a truly useful military leader, making him, for all its might, rather expendable.
Star Wars Legends Candidates Who Would Have Replaced Darth Vader
In Legends, the Empire doesn’t limit the potential power of its non-Sith dark side users, allowing Palpatine to have several potential replacements for Darth Vader on hand before discovering Luke. The Emperor’s adopted daughter, Mara Jade, is easily the most formidable, known as The Emperor’s Hand and working as his personal assassin. One of the Empire’s Inquisitors, Jerec, is not only an exceptionally powerful and learned dark side user, but he also loathes Darth Vader, who wants to supplant him at Palpatine’s side, though his attempts to subvert him were unsuccessful. . Cronal, the prophet of the dark side and director of Imperial Intelligence for short, is another potential replacement for Vader, with his skill at dark side sorcery and deceitful tactics that almost rival those of the two dark lords.
Unlike its canon counterpart, the Legends version of Darth Vader has many dark apprentices, all of which can be used to overthrow Emperor Palpatine. While many serve a purpose other than potential Sith Lordship – Galen Marek is used to wipe out would-be rebels, and Kharys retains an Imperial hold on Skye – one of Vader’s apprentices becomes a real Sith. Lumiya, whose training is ultimately known to Palpatine herself, succeeds Vader and the Emperor and becomes the Dark Lady of the Sith, bringing about the next iteration of the Sith Order after the fragmentation of the Galactic Empire. Palpatine has many potential Darth Vader replacements except Luke Skywalker in both Star Wars timelines, but it’s ultimately Legends-era Lumiya who succeeds both Sith Lords.