In this kind of fanfiction, Sirius Black would be a crucial character. As Harry's godfather, he has a legal claim to Harry's custody. He would be fighting tooth and nail to keep Harry with him. Another important character could be Bellatrix Lestrange. If the Death Eaters have some devious plan involving Harry, she might be involved in the custody battle on Voldemort's side. And of course, Remus Lupin. He's a close friend of Sirius and Harry. He could be an advocate for Sirius' right to raise Harry and also offer his own insights on what's best for Harry.
The key characters could be Harry's muggle relatives. The Dursleys have been his legal guardians in the muggle world for a long time. They might be fighting to keep Harry in their home. On the wizarding side, Hagrid could be important. He was the one who introduced Harry to the wizarding world. He might step in to ensure Harry is placed in a proper wizarding family or environment. Also, Hermione and Ron could play a role. They are Harry's best friends and would surely fight for Harry to be in a place where he can be happy and learn magic freely.
In a 'Harry Potter in a Custody Battle' fanfiction, it might be that Harry's muggle relatives and the wizarding community are in a custody battle. The Dursleys could claim they've been taking care of Harry all these years and have the right to keep him. But the wizarding world, like Hogwarts professors, might argue that Harry belongs with his own kind where he can learn magic and be safe from the threats only the wizarding world understands. There could be courtrooms filled with magic spells and arguments about what's truly best for Harry.
Obviously, Harry Potter is a main character as the title implies he is the one fighting for custody. There might also be his friends like Hermione and Ron who could be helping him out in the battle for custody. Maybe the person or thing he is fighting for custody of could also be considered a main character in a sense, as it's the central object of the story.
Obviously, Harry Potter himself would still be a central character. He would be dealing with the aftermath of the battle, like post - traumatic stress or trying to bring about positive changes in the wizarding world.
Hermione Granger would surely be a key character. She is Harry's best friend and is known for her intelligence. She would use her knowledge of magic and laws to try and stop the execution. Ron Weasley would also be important. He would be by Hermione's side, providing his loyalty and bravery. Neville Longbottom could also play a significant role. He has grown into a strong wizard and might lead the resistance within Hogwarts against the Ministry's decision.
Obviously, Harry Potter himself is a key character as the story is about his release from Azkaban. Dumbledore is likely to be important too. He has the power and influence within the wizarding world to potentially free Harry. His wisdom and knowledge of the situation would play a big role.
Obviously, Harry Potter himself is the central character as the story is about him getting top owl results. Hermione would also be important as she is always the one to help Harry with his studies.
Dumbledore could also be a key figure. He has so much knowledge and wisdom that he might know some ancient magic or spell that could cure Harry. He could guide Harry through the process of getting his health fixed and offer moral support as well.
Dumbledore might play a role. He could be the one who encourages Harry to stand up to the Dursleys. He might have some hidden knowledge about the relationship between the wizarding world and the Dursleys that could help Harry. Also, Hagrid could be involved. He could provide some muscle if things get physical. He might also offer some emotional support to Harry, as he's always been like a big, friendly giant to him.
Well, in such fanfiction, Harry Potter could meet different versions of Dumbledore. In one universe, Dumbledore could be a dark wizard instead of the wise mentor we know. He may also come across alternate versions of Sirius Black. Maybe in some universes, Sirius is still in Azkaban for a crime he actually committed. Additionally, he could meet different versions of Luna Lovegood, some of whom might have no interest in the strange and wonderful things she loves in the original universe.
Voldemort is an obvious one. Given all the destruction and death he has caused, it's very likely that Harry would never forgive him. His actions led to the loss of many innocent lives, including Harry's parents.