Hermione could be another main character. Maybe she discovers what's happening to Harry and the author and tries to find a way to reverse it or at least understand it better. She could use her vast knowledge of magic to research the phenomenon.
Definitely Ginny. Since she's Harry's love interest in the original series, in the fanfiction about them growing up, she has a big role. She could be shown as a strong, independent witch who is equal to Harry in many ways. Draco Malfoy is also a character that features a lot. Sometimes, fanfiction explores his redemption arc further as he and Harry have to interact in the post - war wizarding world.
Hermione could be there. She would be eager to study the different magics and books in Tamriel. Her intelligence would help Harry navigate the new world.
Hermione could be a main character. As a very intelligent witch, she might assist Harry in his teaching, like helping him prepare complex lessons or providing additional knowledge to the students. For example, when Harry is teaching about ancient spells, Hermione could offer insights from the books she has read.
Hermione could be one. She could come to Degrassi to help Harry. She'd be really good at handling the academic side of things there, like helping students with their studies. And also, she could use her magic knowledge to figure out any magical mysteries.
There could be the leader of the coven. This person might be an old and powerful witch or wizard who has been in the coven for a long time. They would be the one to guide Harry into the ways of the coven.
Megatron could also be a major character. Maybe he views Harry Potter as a threat to his power and plans. He could try to either destroy Harry or use his unique abilities for his own evil purposes. And then there could be Bumblebee, who befriends Harry and helps him communicate with the other Autobots, since Bumblebee is often good at making connections.
Hermione could be a main character. She would use her intelligence and vast knowledge of magic to help Harry plan and build the city. Her skills in research and spell - casting would be invaluable.
The elves themselves would be major characters. There could be an elven leader, perhaps an old and wise elf who is the head of the council. Also, Hermione might be involved as Harry's friend and often his partner in adventures. She could bring her vast knowledge of magic and research skills to help Harry in dealing with the council of elves.
Maybe it's about a magical spell that causes Harry Potter and the narrator to age in reverse together. They could relive their past adventures in a new way, with the wisdom of their older selves but the energy of their younger selves.
Hermione Granger would likely be a main character. She could use her vast knowledge to help Harry in his efforts to fix Hogwarts, whether it's researching ancient spells for repairs or coming up with new educational strategies.