Luke Skywalker could be another key character. Since he is Vader's son, his presence could add an interesting dynamic. He might be the one who somehow triggers the battle between Anakin and Vader, or he could be in a position to influence the outcome of their fight, perhaps by appealing to the remaining good in Anakin or by facing off against Vader himself in a three - way struggle.
Well, obviously Anakin and Vader are the main characters. Anakin is his pre - Darth Vader self, full of potential and hope at one point, and Vader is the dark, powerful Sith Lord he becomes.
One interesting plotline could be Anakin's struggle with his past self as Vader. Maybe in the fanfic, Anakin tries to prevent Vader from making the same mistakes he did, leading to intense battles of will and lightsaber duels.
It really depends on how you write it. If it's Anakin at his peak before turning to the dark side, he has a lot of raw power and potential. But Vader has years of experience as a Sith Lord. So, it could go either way.
One idea could be a story that focuses on Anakin's internal struggle between his love for Padme and his fall to the dark side as Darth Vader, while Luke and Leia unknowingly grow up in the shadow of their father's actions. It could explore how their lives might have been different if Anakin had not turned, and how they eventually come to terms with his true identity.
In some fanfics, Anakin's turn to Vader during the Clone Wars might be accelerated by a series of events that test his loyalty more severely. For example, he could be framed for a crime against the Jedi Order. This false accusation could make him feel betrayed by the very people he has sworn to serve. As a result, his connection to the dark side could strengthen as his anger and confusion grow.
In such a fanfiction, one possibility is that Anakin Skywalker might initially be in shock upon seeing Darth Vader. He could struggle to come to terms with what he has become. Maybe there would be a battle of wills as Anakin tries to fight against the dark side within Vader.
Some fanfics take a different approach to Anakin's fall. Instead of it being a complete turn to the dark side, he may be in a more grey area. And Padme is often written as the one who could have pulled him back completely. Luke and Leia in these stories might be more proactive in trying to understand their father's true nature and not just seeing him as the evil Vader. For instance, there's a fanfic where Luke goes on a journey to find out more about Anakin's past before he became Vader, and Leia joins him later. This gives a whole new dimension to their family dynamic.
A possible plot is a fanfic where Anakin, in his Darth Vader form, has a vision of a different future where he didn't lose Padme. This vision makes him question his loyalty to the dark side. Meanwhile, Luke and Leia are on a mission to rescue their father from the clutches of the Emperor. The story could be filled with emotional reunions and battles between the light and dark forces.