Obviously, the slave girl herself would be the main character. She could be from any species in the Star Wars universe, like Twi'lek perhaps, known for being slaves in some parts of the galaxy.
The main character, the slave girl, might be someone who has been in slavery for a long time. She could have unique skills or knowledge that she has gained during her time as a slave. For example, she might be an expert at sneaking around the slave - owners' compounds, which could come in handy later in the story when she tries to escape or help others escape. It's also possible that she has some sort of connection to an ancient power or artifact in the Star Wars lore, which makes her story even more interesting.
The fanfiction might revolve around the slave girl's relationship with the Force. Even though she is a slave, she could be unknowingly attuned to the Force. This could attract the attention of the Jedi or the Sith. If the Jedi find her, they might train her to be a powerful Jedi, using her experiences as a slave to fuel her fight for justice in the galaxy. However, if the Sith get to her first, they could try to corrupt her and use her power for their own evil purposes.
Obviously, the Hutt slave girl herself is a main character. She is often depicted as strong - willed despite her situation. The Hutt lords are also important characters as they are the oppressors. They are usually portrayed as greedy and cruel.
There are also original slave girl characters created by fanfiction authors. These characters can become popular because they represent the struggle against slavery in the Star Wars universe in unique ways, and they often interact with well - known Star Wars heroes or villains in interesting storylines.
A Rebel pilot could be the main character. After getting injured in a battle and having some dental problems as a result, they decide to study dentistry while recovering. They then use their new skills to help their fellow Rebels. They might even find a way to use dental tools as weapons in a pinch, like using a dental drill to break through enemy ship controls if they are captured.
A young scavenger from a planet in the Outer Rim could be the main character. They find the Darksaber by chance and then are thrust into the larger Star Wars universe, having to learn about the weapon and deal with those who would kill to have it.
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.
It could be a former Imperial officer who has seen the error of his ways. After the fall of the Empire, he tries to live a normal life but is drawn back into the conflict when he discovers signs of the Empire's return. He uses his knowledge of Imperial tactics to help the resistance against the returning threat.
An alien species member who has a completely different view of the Force compared to both the Jedi and the Sith. This character could come to the galaxy's main powers and try to change the orders. Their unique biology and culture give them a different perspective on the Force, and they believe that by changing the orders, a new era of peace and understanding can be achieved in the galaxy.
It could be a previously unknown son of Luke Skywalker. Maybe he was hidden away for some reason and now he's lost in the galaxy, trying to find his father or his place among the Jedi.
It could be a young Imperial officer who starts to question the Empire's extreme measures for revenge. This character might see the wrong in what the Empire is doing and eventually defect to the Rebellion.