Well, Archer himself is obviously a main character. He could be a new character inserted into the Star Wars universe. And often, characters like Luke Skywalker or Princess Leia might also be main characters. They could interact with Archer, for example, Luke might be intrigued by Archer's different fighting style and try to incorporate some of it into his Jedi training.
Perhaps the main characters are a group of young Jedi apprentices who have to survive in a 'shattered' Star Wars universe. They might be led by an older, more experienced Jedi who is trying to teach them how to adapt to the new and dangerous situation. There could also be some Sith or dark side characters who are causing more chaos and are the main antagonists for these young Jedi.
I'm not certain, but it might feature a character who has some connection to the shadows, like a Force - user who can manipulate shadows. There could also be an ordinary person who gets caught up in events related to this shadowy aspect of the story.
The main characters are typically the rookie Clone Troopers. They are new to the war and still learning the ropes.
In 'Star Wars Solo: A Star Wars Story', the primary characters are Han Solo, a young and ambitious man looking to make his mark in the galaxy. Chewbacca, the big and furry Wookiee, who becomes Han's close friend and ally. And Lando Calrissian, a smooth - talking and stylish character who owns the Millennium Falcon at first. These characters interact in various ways, driving the story forward with their different personalities and goals.
Often, in 'Star Wars Operation Knightfall Fanfiction', the main characters can include Emperor Palpatine as he is the mastermind behind the operation. Some fanfictions may focus on Anakin Skywalker's transformation into Darth Vader during this time, so he would be a central character. There could also be Jedi Masters and Knights who are trying to resist the Sith's plot. For instance, characters like Obi - Wan Kenobi might be included, as he was one of the few Jedi who survived the initial purge and could be a key figure in a story about the events of Operation Knightfall.
An old Clone Wars veteran, either a clone or a non - Jedi military figure, could be the main character. They have seen the destruction of Order 66 and now suspect there is more to the story with Order 67. Their knowledge of the past wars and military strategies would be useful in uncovering the truth.
There could also be a Sith Lord as a main character. A Sith, by nature, often has a great deal of pride in their power. This Sith Lord could be on a quest to prove their superiority not only to the Jedi but also among other Sith, and their pride could be their most defining and also most dangerous trait.
Often, in addition to the Delta Squad members, other characters from the Star Wars universe may also appear in fanfiction. For instance, they might interact with Jedi Knights. A Jedi could be guiding them in a mission against the Sith or the Separatists. This interaction would be interesting as it would bring together the disciplined clone soldiers and the powerful Jedi with their connection to the Force. Another possible character could be a bounty hunter. The Delta Squad might cross paths with a bounty hunter who is either after the same target or is hired to stop them, creating a tense and action - filled situation.
The main characters could be a group of bounty hunters. They get hired to investigate the origin of Order 69, thinking it might lead to a big payday. As they dig deeper, they find themselves in the middle of a galactic conspiracy. There could also be a Sith apprentice who is using the chaos caused by the order to rise in power within the Sith hierarchy.
Since I haven't read this particular fanfiction, I can't say for sure. But it could be the'son of suns' character as the main protagonist, and perhaps some classic Star Wars characters like Jedi knights or Sith lords who interact with him.