A really cool plot for 'the new sith wars fanfiction' would be to have a hidden Sith cult that has been operating in secret for centuries suddenly emerge during the wars. This cult could have unique Sith teachings and powers that the main Sith order doesn't even know about. The story could follow a group of Jedi and Sith who have to team up, reluctantly, to deal with this new threat.
One idea could be to focus on a young Jedi who is lured to the dark side during the New Sith Wars. Maybe they are promised power to save a loved one. Another could be a group of Sith apprentices vying for the title of the Dark Lord's right - hand, with lots of backstabbing and power plays.
One idea could be exploring the origin of a new Sith Lord. Maybe this Sith Lord has a unique backstory that ties into an ancient Sith artifact, leading to a power struggle within the Sith ranks as others vie for this newfound source of power.
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 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.
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.
Perhaps a Sith uses time travel to obtain ancient and powerful Sith artifacts that were lost in time. This could lead to a power struggle within the Sith order as others vie for control of these newfound items. Well, in this fanfiction scenario, it would add a whole new layer of intrigue and conflict. For example, the Sith who obtains the artifacts might become so powerful that it threatens the existing hierarchy of the Sith, leading to internal battles and betrayals.