Despite being 142 minutes long, The Rise of Skywalker didn't have time explain how the Emperor of the original trilogy managed to survive falling down a bottomless shaft to return thirty years later (I'm of the opinion that it should have been two movies). But now the novelization of the film is ready to hit bookstores, and at least one secret has been revealed.
Although the novelization isn't officially on sale until March 17, Lucasfilm Publishing decided to sell advance copies at this weekend's C2E2 in Chicago and passages have begun appearing online. The book does indeed confirm that the Emperor's spirit has been transferred into a clone body. When Kylo Ren arrives on Exegol and encounters Palpatine, he looks closely at the machinery the Emperor is physically attached to, and recognizes it from his studies of the Clone Wars. He then deduces Palpatine's dark side spirit is too strong for the clone body, and is causing serious degeneration to it.
There's more of an explanation at Screen Rant, although it's not all that satisfying to anyone who wants Star Wars to make complete narrative sense. -via Uproxx