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.
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 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.
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.
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.
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.
Well, Harry Potter would obviously be one of the main characters since it's in the title. There might also be other characters from the original series like Hermione and Ron, but their roles could be altered to fit the 'playboy' theme. Maybe there are new characters created specifically for this fanfic as well.
Hermione would be a great addition. Her thirst for knowledge and love of books would make her very interested in alchemy. She could help Harry decipher the complex alchemical texts. Also, Professor Snape could be involved. Given his expertise in potions, he might have some knowledge or interest in alchemy that could either help or hinder Harry's alchemical journey.
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.
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.
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.