The Dursleys themselves could also be considered important in a way. Their cruel treatment of Harry is what prompts Sirius to act. Vernon, Petunia and Dudley Dursley represent the non - magical, oppressive side of Harry's life. So even though they are not the heroes of the story, they play a role in driving the plot forward by being the reason Sirius takes Harry away.
Obviously, Sirius and Harry are the main characters. Sirius, as Harry's godfather, is the one who takes the initiative to take Harry away from the Dursleys. Harry is the one being rescued, a young wizard who has endured a lot at the Dursleys' place.
There could also be other characters involved. For example, if the fanfic is set in the context of the fight against Voldemort, Dumbledore might make an appearance. He could be a guiding figure in the background, giving Sirius advice on where to take Harry. And perhaps some members of the Order of the Phoenix could be involved too, as they are all in the fight against the dark forces and would be interested in Harry's safety.
In this fanfic, Sirius could be tipped off that the Dursleys are planning to send Harry away to some even worse place. So he swoops in. They flee to a remote wizarding village. There, Harry meets other wizards and witches who are sympathetic to his cause. Sirius helps Harry train in combat magic, as he anticipates future battles. Harry also gets to explore his magical heritage more freely without the Dursleys' restrictions.
The main characters are Harry, who has reached his breaking point with the Dursleys. His pent - up anger and frustration towards them finally explodes into action. The Dursleys, on the other hand, are the recipients of Harry's wrath. Uncle Vernon, with his blustering and bullying ways, Aunt Petunia, who has always been cold and distant, and Dudley, the spoiled brat. There could also be appearances from characters like Dumbledore, who might show up to either reprimand Harry or offer some kind of guidance depending on the nature of the attacks.
One possible reason could be that Sirius, being Harry's godfather, feels it's his right and duty to protect Harry. He might not trust Hagrid fully to keep Harry safe, especially considering the dangerous situation Harry is in. Sirius has a strong connection to Harry and wants to be directly involved in his upbringing and protection.
In many of these fanfics, there could be a new character introduced, like an old wizard who lives in the neighborhood secretly and notices Harry's situation. This character might play a crucial role in helping Harry deal with the Dursleys and his growing magical powers. He could be a mentor figure for Harry, guiding him through the tough times.
Obviously, Harry Potter is the main character as it's about him taking control. Hermione Granger is likely to be an important character as well, she would probably be by Harry's side, offering her intelligence and support.
A rogue wizard who has his own ideas about Harry's future could take him. This wizard might think that he can better prepare Harry for the fight against Voldemort than Dumbledore or the Order of the Phoenix.
Well, Harry Potter is surely one of the main characters since the title implies it's about him being taken from the Dursleys. There might also be some original characters created by the fanfiction writer to play important roles in Harry's new journey.
It's also likely that they go to Romania. Given Sirius' knowledge of the wizarding world, he might know of a safe haven there. In Romania, they could be around dragons and learn about dragon - related magic. Harry would surely be fascinated by the dragons and it could be a place where he can grow stronger in a different kind of magical environment.
Obviously, Harry would be one of the main characters.
Obviously, Harry Potter is a main character as the title implies. But usually, his friends like Hermione and Ron are also likely to be important. They would be there to support Harry in his new role of taking control.