Well, the uniqueness might lie in the combination of the 'Star Wars' universe's rich lore and the specific nature of the Seventh Sister's role. If it's a lemon fanfic, it might also add a different layer of relationships and interactions that we don't typically see in the official 'Star Wars' media. For example, it could explore her relationships with other characters in a more intimate or emotional context that is different from the usual action - adventure focus of the series.
The Seventh Sister is a significant character in 'Star Wars Rebels'. She is part of the Inquisitorius, which serves the Galactic Empire. Her character design is quite distinct. She is highly skilled in combat, using her lightsaber with great proficiency. She is involved in many pursuits of the rebels and their Jedi allies. For example, she once cornered Ezra Bridger during a mission. Her presence adds to the sense of danger and threat that the rebels face.
It could be a story full of action and adventure. The Seventh Sister, with her lightsaber skills, and Erza, with her magic and sword - fighting abilities, could join forces to fight a powerful enemy. This enemy could be a dark wizard in Erza's world or a new Sith - like threat in a combined universe. Their combined powers would make for some epic battles and a really exciting fanfiction.
There's a fanfiction where the Seventh Sister teams up with the Rebels against a common enemy, a powerful Sith Lord who is trying to take over the galaxy. In this story, she realizes the wrongdoings of the Empire and decides to fight for a greater good. It has a lot of action scenes and interesting character interactions.
I'm not sure of specific 'Star Wars Rebels Seventh Sister' lemon fanfics off the top of my head. You could try searching on fanfic platforms like Archive of Our Own. They usually have a wide variety of fan - created stories.
The mystery around her character. In the series, we don't get a full picture of her past. Fanfiction fills that gap. For example, some fictions explore her relationship with other Inquisitors.
One possible plot is that the Seventh Sister gets lost in a different dimension and ends up in Erza's world. She is confused and starts causing trouble, but Erza tries to reason with her. Eventually, they find a way to send the Seventh Sister back home, but not before they form a bond of mutual respect.
One common theme is redemption. Since she's a Sith assassin, many fanfics explore the possibility of her turning away from the dark side. Another theme is her loyalty to the Empire and how it can be tested. For example, in some fanfics, she has to choose between her loyalty to the Sith and her own moral code.
It could be a slaver boss. This character might be someone who has a network of slaves and sees the Seventh Sister as a valuable asset. He is cruel and only interested in profit. He would constantly try to break her spirit and force her to do his bidding. Maybe he also has some knowledge of the Force that he uses to keep her in check. Also, it could be an alien warlord who enslaves the Seventh Sister to fight in his gladiatorial arenas, seeing her as a great addition to his entertainment.