Emperor Palpatine lived, after a fashion, and Kylo could feel in his very bones that this clone body sheltered the Emperor's actual spirit. The liquid flowing into the living nightmare before him was fighting a losing battle to sustain the Emperor's putrid flesh. He'd seen this apparatus before, too, when he'd studied the Clone Wars as a boy. Here it is: All the vials were empty of liquid save one, which was nearly depleted. The detail about Palpatine being a clone comes in the description of the machinery and equipment attached to Palpatine. The excerpt from the Star Wars: The Rise of Skywalker novelization was posted at ScreenRant, and it comes early in the book when Kylo Ren arrives on Exegol and meets Palpatine in-person. It turns out that Emperor Palpatine is a clone in Star Wars: The Rise of Skywalker.