This article contains spoilers for Star Wars: Hidden Empire #2.Star Wars has confirmed Palpatine wasn't actually a Sith Lord at all - and he knew it. He may have been considered the pre-eminent Sith Lord of the original trilogy, but it's long been clear Palpatine's relationship with the Sith was somewhat unorthodox. Darth Sidious played fast and loose with the Rule of Two; there's some evidence he may have actually trained Darth Maul and Count Dooku simultaneously. His greatest apprentice, Darth Vader, even accused Palpatine of being a Sith heretic due to his willingness to combine technology and the Force. The Emperor would ultimately use such a heretical approach to conquer death itself, with his spirit occupying a clone body on the Sith redoubt of Exegol.
Star Wars: Hidden Empire #3, by Charles Soule and Steven Cummings, suggests Palpatine came to consider himself very different to the Sith. Set between The Empire Strikes Back and Return of the Jedi, the story sees the Emperor's enemies attempt to unleash a new threat to his reign - an ancient Sith Lord who has been frozen in time. Briefing Darth Vader on this potential rival, Palpatine reflects on the nature of the Sith. "The Sith Lords were a varied lot," he observes, "but all of them sought the same thing... dominion." It's striking that Palpatine refers to the Sith Lords in the past tense, as though they no longer exist.
Had Palpatine Destroyed The Sith As Well As The Jedi?
To be fair, is possible Palpatine is simply referring to the Sith Lords who existed before Darth Bane established the Rule of Two. Darth Bane slaughtered the remaining Sith Lords and reformed the Order; Palpatine could well consider the Baneite Sith so different to their predecessors that they are essentially a separate entity. But this interpretation of the line seems unlikely, given Star Wars: The Clone Wars stressed a line of continuity running through these two incarnations of the Sith. Rather, a more likely interpretation is that Palpatine had indeed come to believe the Sith were a thing of the past.
Palpatine was a supreme egotist. He considered himself the culmination of a millennium of Sith scheming, greater than anything that had gone before. He certainly still considered himself a Sith at the time of Star Wars: Episode III - Revenge of the Sith, but his victory over the Jedi could well have gone to his head. That would explain why he began to play fast and loose with Sith doctrines, pursuing strategies that would be considered heretical. Palpatine failed to take an apprentice after Return of the Jedi, concerned with restoring his own failing health rather than passing on his teachings and thus preserving the line of the Sith. Meanwhile, it's interesting to note he even seems to have stopped going by his Sith name; there's no mention of "Darth Sidious" in the original trilogy or even in the sequels, with Palpatine dropping this as a now-unnecessary alias. Such a decision runs counter to every tenet of Sith faith, because to a Sith their "Darth" name is supposed to be their true identity.
This argument is strongly supported by Star Wars Rebels, most notably by the tremendous episode "Twin Suns." This saw Darth Maul successfully track Obi-Wan Kenobi to Tatooine, where the two confronted one another. The episode deliberately paralleled the two, presenting them as relics of the past - one a former Sith Apprentice, the other the last Jedi Master. Maul's final words spoke of Luke Skywalker; "He will avenge us," he declared, believing Palpatine's rule would be overthrown by the one he believed to be the Chosen One. Maul seemed to believe Palpatine had destroyed Jedi and Sith alike, leaving something else in their place - something that had grown out of the Sith, but that considered itself greater. He may have been the greatest villain of Star Wars, but Palpatine's being a Sith may have become a lie.