Power struggle is a very common theme. The OC often has to deal with the power - hungry Sith and find their place in the hierarchy. Another theme is redemption. Sometimes the OC tries to bring some good to the Sith or find a way to break free from the dark side.
One popular 'oc sith crossover fanfiction' is 'The Sith Apprentice's New Path'. In this fic, an original character gets thrown into the Sith world and has to navigate the dark side politics. It has great character development.
One great Sith crossover fanfiction is 'Sith in the Star Trek Universe'. It's really interesting as it combines the dark and powerful Sith with the sci - fi world of Star Trek. The Sith's use of the Force and their complex power struggles play out in a new and exciting way against the backdrop of the Starfleet and alien species in Star Trek.
One memorable OC Sith could be Darth Zyra. She has a very distinct look with her purple - hued lightsaber and her elaborate black and red robes. Her power lies in her ability to manipulate the minds of her enemies, which she uses to great effect during battles in the Clone Wars.
First, know your source materials well. You need to understand the lore of the Sith from Star Wars, as well as the other universe you're crossing over with. For example, if it's with Harry Potter, know how magic works in both. Then, create a strong plot. Maybe the Sith are searching for a powerful artifact in Hogwarts. And don't forget to develop your characters. The Sith should have their own motives and personalities that are consistent with their Star Wars roots.
One possible fanfiction could be about a Sith Lord from Star Wars ending up in the Naruto universe. Maybe he tries to use the Force to control the chakra, but finds that it's a completely different power system. He could then form an alliance with some of the villains in Naruto, like Orochimaru, who are also interested in power and dark arts.
One great 'oc sith fanfiction' story could be about an OC (original character) Sith who struggles to rise through the ranks in the Sith hierarchy. This character might face challenges from other Sith Lords who see them as a threat. Another interesting one could be an OC Sith's journey to discover an ancient Sith artifact and the battles they have to fight along the way.
One idea could be that a Sith Lord somehow gets transported to the MCU universe and tries to take over Hydra. They could use their dark side powers to manipulate the already corrupt organization. Another could be a story where a young Jedi in training from the Star Wars universe ends up in the MCU and teams up with the Avengers to fight a Sith who has also made their way there. Maybe they have to combine the Force with the superpowers of the Avengers to defeat the Sith.
One possible scenario could be Ruby's struggle with the dark side. As a Sith, she might initially be drawn to the power it offers. For example, she could use her newfound Sith abilities to fight Grimm more effectively in the RWBY universe. However, she would also face the internal conflict of losing her former self. Her friends in RWBY might try to bring her back from the dark side, similar to how characters in Star Wars try to redeem fallen Jedi or Sith. This could lead to intense battles and emotional confrontations within the story.
One idea could be a crossover between a Sith Lord and a superhero universe. The Sith Lord's dark powers and manipulation skills would create an interesting dynamic against the heroes. For example, a Sith Lord in the Marvel Universe could try to turn some of the anti - heroes to the dark side.