One great Sith Ahsoka fanfic is 'The Dark Path of Ahsoka'. It explores an alternate universe where Ahsoka turns to the Sith side. The story is filled with intense battles and moral dilemmas as she struggles with her new identity.
She could be developed through her interactions with Sith apprentices. Maybe she tries to redeem one of them, showing her compassion and strong will. This would also show her growth from her Jedi training.
I'd recommend 'Sith Apprentice: Legacy of the Dark Side'. It's a story that focuses on an apprentice who discovers an ancient Sith artifact and the chaos that ensues. It's full of mystery and action.
The setting of the fanfic is important too. If it's set in a new part of the Star Wars universe, it should be described vividly. For a Sith Ahsoka, perhaps it's a dark and desolate planet where she trains in the Sith arts. The descriptions of her using Sith powers, like lightning or mind control, should be exciting and not just a rehash of what we've already seen in the movies. Also, the fanfic should have some sort of conflict, not just internal conflict within Ahsoka but also external, like a fight against the Jedi or other Sith who oppose her new - found power.
Another theme could be redemption. In many Ahsoka Sith fanfic, even if she dips into the dark side, there is often a path towards redemption. It shows that no matter how far one falls, there is always a chance to come back. This can be a very powerful and inspiring theme, as it gives hope to the characters and the readers alike. Also, the exploration of power is a theme. The Sith are known for their pursuit of power, and when Ahsoka gets involved with them, she may be tempted by the promise of greater power, which can lead to many different plot developments.
A popular one is 'The Sith Apprentice's Trial'. In this fanfiction, the apprentice has to face numerous challenges to prove their worth in the Sith order. It has some really cool battle scenes and explores the darker aspects of the Star Wars universe in an interesting way.
One idea could be that she is influenced by a powerful Sith artifact. Maybe she discovers an ancient Sith holocron that slowly corrupts her mind, making her question her Jedi teachings. This could lead to her making small compromises in her beliefs until she gradually slips towards the dark side.
Ahsoka as a Sith would have a different fighting style. She would be more aggressive and use more Sith - inspired powers. Her lightsabers might even change in appearance, perhaps taking on a more menacing red glow. She would also start to form alliances with other Sith or dark - side characters, which would change the power dynamics in the galaxy.
One plot idea could be Ahsoka being tempted by the dark side by a Sith. Maybe she is lured with the promise of greater power to defeat an enemy. Another could be a Sith trying to use Ahsoka as a pawn in a larger scheme against the Jedi Order.
One interesting storyline could be Ahsoka being forced to team up with a Sith to fight a greater evil. Maybe they start off distrusting each other but gradually come to respect one another's skills.