There might also be some new or minor characters from the wizarding world that are introduced specifically for this fanfiction. For instance, an old healer who has a unique method of restoring eyesight that no one else knows about. This character could play a crucial role in Harry being able to see again.
Dumbledore could play an important role too. Even though he's passed away in the original series, in fanfiction, his spirit or his past actions could be related to Harry's inheritance. He might have left some clues or instructions for Harry to find out about his true inheritance.
Hermione would probably be involved. She's always been there for Harry in the original series, so in this fanfiction, she might be the one trying to find a way to reverse the situation or help Harry through the process. She's smart with potions and magic, so she'd be a key character.
One main character could be Griphook. He already has a complex relationship with Harry Potter in the original series. In a goblin rebellion fanfiction, he could be a key figure leading the goblin revolt, using his knowledge of the wizarding world and his own skills to strategize against the wizards. Another character could be a young goblin apprentice who is caught between his loyalty to his own kind and his admiration for Harry Potter and the wizarding world.
Hermione Granger is often involved. She's Harry's best friend and is extremely intelligent. Her knowledge of spells and magic history can be crucial in helping Harry prove his innocence. She might research old laws or spells that can be used as evidence.
Often, we might see characters like Harry Potter himself getting involved in investment - related activities. He has the fame and the knowledge of the wizarding world that could be useful. Hermione Granger could also be a main character in such fanfiction, using her intelligence to analyze investment opportunities. Ron Weasley might tag along, perhaps bringing in his unique perspective on the wizarding market.
The Weasley twins could be part of it too. Suppose Harry yells in excitement or anger about a new prank idea that the twins have come up with that might be a bit too dangerous. They could either encourage his yelling or try to tone it down, depending on their mood. And Malfoy might overhear Harry's yell and use it as an opportunity to taunt him, adding more conflict to the fanfiction.
Another character could be Draco Malfoy. There could be fanfiction where Draco, having been on the wrong side for a long time, now has a change of heart and wants vengeance against his own family or the Death Eaters who used him. He might use his knowledge of the Dark Arts that he learned from his family, but now turn it against them in a bid for redemption through vengeance.
Obviously, Harry Potter himself is the central character as it's about him in diapers. Dumbledore often features as he plays a crucial role in Harry's life. Hagrid might also be there as he has a special connection with Harry. And of course, the Dursleys could be part of the story, perhaps in their begrudging care of baby Harry.
Harry Potter himself could be one of the main characters in such fanfiction. Maybe he gets an automail limb after a particularly dangerous encounter with Voldemort. Hermione might also be involved, using her vast knowledge to help understand and improve the automail technology within the wizarding context.
Harry Potter himself is often a central character. Since he was the one destined to defeat Voldemort and destroy the Horcruxes in the original story, many fanfictions continue his journey with Horcruxes in new and different ways. Hermione Granger also features prominently. Her intelligence would be crucial in understanding the nature of Horcruxes and finding ways to deal with them.