One plot idea could be Rey being tempted by the dark side and Sith teachings in a more psychological way. Maybe she starts having visions of past Sith Lords who try to convince her that the power they offer can help her protect the galaxy more effectively. Another could be a story where Rey discovers a hidden Sith artifact that has the power to either corrupt or be redeemed, and she has to make a choice about what to do with it. A third idea is that Rey has to face a new Sith threat that is related to her own past in some way, like a long - lost Sith relative or a Sith cult that was involved in her family's history.
Well, she could be kidnapped by a group of Sith cultists who believe she has the potential to become a great Sith. They subject her to various tests and trials, trying to break her spirit and turn her. Or perhaps Rey discovers an ancient Sith holocron that shows her an alternate version of the Star Wars universe where the Sith won. This makes her question her own beliefs and path. Also, a plot could involve Rey accidentally using Sith magic while trying to master new Jedi skills, which sets off a chain of events that attract the attention of the remaining Sith in the galaxy.
A possible plot is that Rey, in her quest to understand the Force better, stumbles upon a Sith temple. Inside, she finds a Sith apprentice who was left behind ages ago. The apprentice tries to manipulate Rey into believing that the Sith way is the true way to balance the Force. Another idea is that Rey starts having dreams where she is a Sith. These dreams become so vivid that she begins to doubt her identity as a Jedi. She then embarks on a journey to find out if there is some truth to these dreams, and if she has a connection to the Sith that she doesn't know about.
One idea could be that Rey discovers she has a hidden connection to the Kenobi family. Maybe she finds an old Jedi artifact that was once Kenobi's and it unlocks memories or powers within her. Another plot could involve Rey traveling to a planet that was important to Kenobi and uncovering secrets there.
One idea could be that Anakin's spirit somehow guides Rey in her Jedi training. Maybe he appears to her in visions and imparts his unique knowledge of the Force, especially the more unorthodox aspects he learned during his time. Another plot could involve Rey finding an ancient artifact that was once connected to Anakin, and through it, she uncovers secrets about his past that help her in her fight against the new Sith threat.
A possible plot in Rey Skywalker fanfiction is that Rey discovers an ancient prophecy related to the Skywalkers that foretells a great danger to the galaxy. She then has to gather allies, both old and new, to prevent this catastrophe. Along the way, she might have to deal with her own self - doubts as she tries to figure out how being a Skywalker affects her role in this prophecy. She could also face internal struggles as she tries to balance her Skywalker heritage with her own unique identity as a former scavenger.
Perhaps a Sith Lord is kidnapped by a mysterious cult that worships an ancient and powerful force entity. The Sith Lord has to use his wits and dark side powers to escape while also trying to figure out the cult's motives. This could involve battles with strange cultists and uncovering dark secrets.
Perhaps a Sith Inquisitor is sent on a mission to hunt down a Jedi who has some knowledge that could undermine the Sith order. Along the way, he starts to question the Sith teachings. He could meet some interesting characters during his hunt that make him see things differently. For example, he might encounter a group of rebels who are fighting for freedom, and this makes him wonder if the Sith way is truly right. As he gets closer to the Jedi, he has to battle his own inner demons as well as the physical threats that come his way.
Perhaps a fanfiction where Anakin, as a Sith, is sent on a mission by Palpatine. But on this mission, he meets a young Force - sensitive who reminds him of his own past. This makes him start to have doubts about the Sith ways. He begins to secretly teach the young one about the Force in a more balanced way, all while trying to hide it from Palpatine.
One idea could be a young Jedi who falls to the dark side and starts to gather a harem of Sith apprentices, each with their own unique skills and backstories. They could all be on a quest to find an ancient Sith artifact that is said to grant ultimate power.
One idea could be exploring what would have happened if Anakin had a different mentor during his fall to the dark side. Maybe a Jedi who was more in tune with his emotions could have guided him better.
One plot idea could be a Sith Pureblood rising through the ranks in the Sith hierarchy during the Clone Wars. They might start as an apprentice and have to prove themselves by undertaking dangerous missions against the Jedi. For example, they could be tasked with infiltrating a Jedi stronghold to steal a valuable artifact. Another idea is a story about a Sith Pureblood who has a change of heart and tries to defect from the Sith. This would involve a lot of internal struggle as they fight against their dark side training and the fear of reprisal from the Sith Lords. A third plot could revolve around a group of Sith Purebloods who form a secret society within the Sith order, with their own goals and agendas that may or may not align with the overall Sith plans during the Clone Wars.
Another idea is that the Sith Empire decides to use a new form of Sith magic during the Clone Wars. This magic starts to corrupt the planets it is used on, and the Jedi have to find a way to stop it. The story could show the different reactions of various species to this new threat. For example, some might be more susceptible to the corruption while others are more resistant. The Jedi would have to form alliances with these different species to combat the Sith Empire's new weapon. This would involve a lot of political maneuvering as well as physical battles. It could also explore the nature of the Force and how the Sith's use of it in this new way affects the balance.