Luke Skywalker's Force ghost haunted Kylo Ren in Colin Trevorrow's version of details on Trevorrow's Star Wars 9 are coming out.
Ben Solo is redeemed and ultimately sacrifices himself to save Rey (and the galaxy). However, in Duel of the Fates, any attempts to save Ben are unsuccessful, and he dies as a ruthless villain. Kylo was in a truly disturbed place, as evidenced by more Duel of the Fates reveals.
Per Collider, Kylo's main mission in Duel of the Fates was to "end the Jedi and Sith once and for all." At the start of the film, he was "wallowing around in Vader's old castle" on Mustafar, even battling a hallucination of his grandfather at one point. Even more interesting is the revelation Luke's Force ghost haunted Kylo, which connects to Skywalker's "See you around, kid" line at the end of The Last Jedi.
Force ghosts are one of the most famous Star Wars tropes, dating back to The Empire Strikes Back in 1980. Typically, they appear before their former students during times of need, offering words of wisdom and encouragement (a la Obi-Wan in the original trilogy and which was a reshoot, ended up being one of the more controversial in the final film since some interpreted it as a rebuke of The Last Jedi.
There isn't anything wrong with Force ghost Luke helping Rey get back on track, but Trevorrow's take certainly feels like a missed opportunity. Luke and Kylo had a truly fascinating dynamic in the sequel trilogy, and it would have been interesting to see more interactions between the two. The Last Jedi seemed to set something up with Luke and Kylo for the next film, but The Rise of Skywalker doesn't do anything with that thread (instead basing Kylo's arc on his conflicted feelings over murdering Han Solo). Perhaps someday fans will get to see a dark side haunted by a Force ghost. It seems like an idea too good to up.
Source: Collider