There could be an original character created specifically for this fanfiction. This character might be the one directly affected by the 'ghost of you', and through their story, we get to explore the new ideas and plotlines in this fan - made story.
Hermione might also be a main character. She's known for her intelligence and problem - solving skills. In this fanfiction, she could be trying to figure out the mystery behind the 'ghost of you' phenomenon, using her vast knowledge of magic and lore.
Hermione would likely still be a main character. She would probably be the one trying to research about Harry's half - ghost condition, scouring the library for any information on half - human, half - ghost beings in the wizarding world. She might also be the one to help Harry control his new abilities when they get out of hand, using her vast knowledge of magic.
Since I haven't read it, I can't say for sure. But it's likely to feature Harry Potter, Hermione Granger, and Ron Weasley as they are the central characters in most Harry Potter - related stories. There might also be other characters like the goblins from Gringotts who would be important in a story about banking in the wizarding world.
I think Luna Lovegood would make an excellent main character in a Harry Potter Ghost Hunters fanfic. She already has a very open - minded view of the magical world and is quite in tune with the more ethereal aspects of it. Fred and George Weasley could also be main characters. Their mischievous nature would lead them to be interested in ghost hunting, and they could use their inventions to help in their investigations. Additionally, Ginny Weasley could be part of the group, being brave and having her own experiences with the supernatural at Hogwarts.
Neville Longbottom could be a central figure in some Harry Potter Rebels fanfiction. He has shown great courage and the ability to stand up against the dark forces. In fanfictions, he might lead a rebellion against some corrupt elements in the Ministry of Magic. His growth from a shy boy to a brave hero in the original series gives him great potential to be a main character in these rebellious stories. And Luna Lovegood could also be important, with her unique perspective and disregard for convention, she could inspire others to rebel in the fanfiction world.
Another possibility is a new character created specifically for this fanfiction. This character could be a scientist or a wizard from a different part of the world who has knowledge of both nanotechnology and magic, and they bring the concept of nanobots into the Harry Potter universe.
Obviously, Harry Potter and Marris are the main characters. Harry is the well - known boy wizard, and Marris is the character specific to this fanfiction. There may also be other characters from the original Harry Potter series like Hermione and Ron, who might play supporting roles in the fanfiction.
Obviously, the grandchildren of Harry Potter are main characters. They often have names that are related to the Potter family traditions. There could also be their friends at Hogwarts, who might be from different wizarding families or even Muggle - borns.
Most likely, Harry Potter would still be one of the main characters. Since it's in the Harry Potter universe, he's central to the story. He could be the one around whom the new bonds are formed or strengthened.
In addition to the ones mentioned, Dumbledore could be a main character in some fanfictions. He knew Flamel, so he could play an important role in stories about Flamel. Voldemort could also be a main character as he was after the Philosopher's Stone, and his actions could be intertwined with Flamel's story. There could also be original characters created by the fanfiction authors who interact with Flamel and the other known characters.
There could be new characters created specifically for this fanfiction that are central to the merging concept. For example, a character who has the ability to control the merged magic or someone who is the key to uniting different groups of wizards that were brought together in this fan - made story.