A popular fan theory about Star Wars: The Rise of Skywalker states that rather than Palpatine having been the apprentice of Darth Plagueis the Wise, the Sith Lord actually was Plagueis himself.
The theory goes back to Revenge of the Sith, where Palpatine tells Anakin of his former master who became able to use the Dark Side to cheat death, which Rise revealed as ‘Essence Transfer,’ the relocation of a spirit into another vessel. This recontextualizes the Rule of Two – that there can only ever be one pair of Sith, master and apprentice – to be that when the apprentice turns on the master and attempts to strike them down, this allows them to possess the younger form, becoming immortal through parasitic body hopping, and that this was what Plagueis did.
However, a passage from the fan-angering novelization of The Rise of Skywalker puts paid to the theory, providing some background information missing from the movie, where Rey experiences Palpatine’s memories of his original death at the hands of Darth Vader at the climax of Return of the Jedi.
“Falling… down a massive shaft, the betrayal sharp and stinging, a figure high above, black clad and helmeted and shrinking fast. His very own apprentice had turned against him, the way he himself had turned against Plagueis… whose secret to immortality he had stolen. Plagueis had not acted fast enough in his own moment of death. But Sidious, sensing the flickering light in his apprentice, had been ready for years. So the falling, dying Emperor called on all the dark power of the Force to thrust his consciousness far, far away to a secret place he had been preparing. His body was dead, an empty vessel, long before it found the bottom of the shaft, and his mind jolted to new awareness in a new body – a painful one, a temporary one.”
Specifically, the paragraphs reference Palpatine and Plagueis as two separate individuals, meaning that while it was an interesting idea to imagine the Sith power being retconned like Jason Voorhees’ heart in Jason Goes to Hell, the canon explicitly states this to not be the case.
It’s been months now, and the narrative inadequacies of Star Wars: The Rise of Skywalker are still leading to discussions and arguments about what is and isn’t accurate regarding all the details that the film didn’t bother to impart. This one, however, can now be put to rest.