An older, wiser mentor figure could be included. This person has seen the world and can offer Harry advice on how to grow out of his playboy phase. They could have a backstory of their own, like they were once a playboy or knew someone who was and learned from their mistakes. For example, he could be an old actor who has retired from the limelight and now wants to help the younger generation.
One of the main characters could be a Protoss high templar. This character could be the one who first discovers Harry and decides to take him under his wing. Another could be a Protoss zealot, who is initially skeptical of Harry but later becomes his ally in battles.
His family members might also be important characters. His parents, if they are alive in the fanfic, could be the opposite of Harry when it comes to snow. They might be the ones who want to take family pictures in the snow every year, and Harry dreads those moments. Or a younger sibling who is always excited about snow and can't understand Harry's dislike.
Ron could also be a major character. He might have a hard time accepting Harry as a girl at first. But as the story progresses, he could become more understanding and protective of Harry in this new form. And there could be some really funny and awkward moments between them.
Sirius Black would be an interesting character to put in the fanfiction. He has his own history with the dark arts and could offer a different perspective on Barty's actions. And Neville could also be included. His growth and courage could inspire both Harry and Barty in different ways. Neville might stand up to Barty in a situation where others might not, showing his new - found confidence.
Hermione could be one of the main characters. She might be suspicious of Orochimaru's teachings and try to convince Harry that it's wrong. She would be constantly researching about Orochimaru and the type of magic he's teaching Harry to prove her point.
I think Luna Lovegood would be an interesting character to include. Her unique perspective on magic and the world around her could add an element of mystery and wonder to the fanfiction. Also, Severus Snape. His complex past and relationship with both Harry and Tom (in a way, as Tom became Voldemort) could bring a lot of depth to the story. And Hagrid, who could provide a connection to the more gentle and nurturing side of the wizarding world, which might be important for Harry and Tom's relationship development.
For a more villainous touch, including Voldemort or his followers could create high - stakes situations. Bellatrix Lestrange could be a terrifying adversary for Harry and Gabi. On the other hand, adding new original characters, like a powerful but reclusive wizard who lives in the Forbidden Forest, could also make the story more exciting.
Dumbledore. His vast knowledge of magic and the wizarding world could play a crucial role. He might have some prior knowledge about the origin of the creature situation involving Harry and Voldemort. He could also offer guidance and wisdom, perhaps even try to find a way to use the situation to finally defeat Voldemort in a more permanent way.
Hermione could be included. She might be suspicious of Harry's interactions with Bellatrix and try to interfere or help, depending on the situation. Her intelligence could also be crucial in understanding any strange magic related to Bellatrix.
Hermione could be one of the main characters. She might be the one who tries to find Harry and bring him back. She would use her intelligence and knowledge of magic to track him down, all while worrying about his safety.