Star Wars: Dark Empire is the epic comic series from Dark Horse Comics that was one of Star Wars' fans first ever looks at the events that occurred after Return of the Jedi. At the time, Dark Empire was canonical, showcasing the adventures of Luke, Leia, and Han as they continued to fight the Imperial Remnant across the stars in order to create the New Republic. Luke Skywalker's journey after Episode VI in this story was particularly challenging, as the lure of the dark side became too much for the young Jedi, leaving him no choice but to become the apprentice of a reborn Emperor in this incredible story that has now become a Star Wars Legend.
Dark Empire came from the minds of Tom Veitch and Cam Kennedy in the early '90s from Dark Horse Comics, taking place just six years after the events of Return of The Jedi where the second Death Star, Darth Vader, and the Emperor were all destroyed. During this time, the Rebel Alliance has become the New Republic, and are hard at work battling the remaining Imperial forces scattered across the galaxy. Luke Skywalker's power has grown as well, now able to take down an entire Imperial walker with ease. However, Luke begins to feel the pull of the dark side. Fearing for the safety of his sister and allies, Luke heads towards the source of the dark side's call.
Shockingly, Luke finds himself face to face with none other than the Emperor reborn, having attained a form of immortality through the dark side, transferring his spirit in the Force into waiting clone bodies he has created. Obviously, this was an element that Disney decided to adapt after its purchase of the Star Wars franchise, which they used in The Rise of Skywalker, despite purging the books and comics that predated 2014 from the canon and timeline, labeling them as Legends. Regardless, Luke's journey is incredibly dynamic and engaging, as the Emperor offers Luke a place at his side, seeing him as a far more powerful and suitable apprentice than Vader ever was. In the face of the Emperor's power, Luke believes he can experience the dark side without fully embracing it, allowing him to destroy the Emperor from within. In his flawed thinking, Luke agrees and becomes the Emperor's new apprentice.
Of course, Luke underestimated the lure and temptations of the dark side and its ability to so easily corrupt. Eventually, Luke was unable to resist, and truly did become Palpatine's new apprentice, experiencing new levels of power he'd never known before that Vader could never have attained. However, Leia was strong in the force as well. Unlike in Rise of Skywalker where it was revealed that Leia abandoned her Jedi training for the sake of her son, Dark Empire's version of Leia was still training to become a Jedi, and was determined to bring her brother back to the light. Luke and Leia crossed lightsabers in front of the Emperor, whose true desires were revealed, seeking to inhabit and possess Leia's powerful unborn child. However, Leia manages to break through the dark side's influence over Luke, showing him the bright future that she's seen: Her brother training all of her children to be strong and courageous Jedi (she would have three in the Legends timeline).
Strengthened by his sister's words, Luke fights back against the Emperor, who had unleashed a chaotic storm of dark side energy that not even he could fully control. Working together, the Skywalker siblings cause that same energy to overtake Palpatine, which destroys him - for the time being. Having been brought back to the light by Leia, Luke announces that the Jedi will rise again, intending to restart the New Jedi Order.
While this of course has now been rendered non-canonical, it's not hard to see the places where Disney used and adapted quite a few elements from the massively popular series for their new Sequel Trilogy. However, it would have been extremely interesting and huge if Disney had decided to make Luke's temporary turn to the dark side canonical as well. Luke explains to his sister that part of his choice to become the Emperor's apprentice was due to his need to know why their father chose the dark side, learning that it was the result of fear and the tempting promise of power to combat it. In this way, Luke's destiny did indeed become that of his father Darth Vader, redemption and all. Despite now being a Star Wars Legend, it may be one of the best ones in the entire Star Wars galaxy and is thus worth remembering.