So even though Rey, Finn, Poe Dameron and the rest of the main characters who have headlined this latest Star Wars trilogy will still be running the show, things and events from before their time will factor into The Rise of Skywalker’s story. That includes, as arguably the biggest Episode IX surprise from today, the return of Emperor Palpatine. His sinister laugh was heard at the end of the preview, and if Ian McDiarmid appearing on stage after the trailer screened at Star Wars Celebration wasn’t proof enough, it was confirmed later that the actor is indeed reprising the Sith Lord, though it remains to be seen if Darth Sidious has somehow returned to life or if we’ll be seeing him through flashbacks, holograms, as a Force ghost, etc.
Article source: https://www.cinemablend.com/news/2470278/why-star-wars-episode-ix-is-called-the-rise-of-skywalker-according-to-jj-abrams