Harry himself could be the main character. Since it's a Harry Potter fanfiction, it's likely that he plays a central role. Maybe he's trying to impress Ginny by bringing her flowers in a very magical and unexpected way.
Well, it could be about a story in the Harry Potter universe where someone asks Harry to just bring them flowers. Maybe it's a romantic gesture towards a character, or it could be part of a magical plant - related plot. For example, perhaps the flowers have special properties in the wizarding world and are needed for a spell or to cure an ailment.
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.
Neville Longbottom could be a main character. He has always had the potential for great things and in a world without Harry, he would be likely to step into the spotlight. He has the courage and the connection to Hogwarts that could make him a central figure in the fight against evil.
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.
Hermione could also play a role. Given her intelligence and love for learning, she might take an interest in accounting to better manage the finances of the various causes she's involved in, like the Society for the Promotion of Elfish Welfare. So she could be a main character or at least a supporting one in this fanfiction.
Obviously, Harry Potter himself could be a main character. He could be the one who is initially reluctant to participate in a dance event but then discovers a new passion for it. Hermione could also be a main character as she might be the one researching the history and significance of different wizarding dances.
In addition to the main trio from the Harry Potter series, there could be some of the Hogwarts professors as main characters. For example, Professor Dumbledore might have some knowledge about the balverines that he imparts to Harry. And Hagrid, with his love for all kinds of strange creatures, could be involved in trying to tame or at least understand the balverines better.
Harry, Hermione and Ron could be the main characters, exploring the mysteries of the mansion. Or perhaps a new generation of wizards, like the children of the original trio. Neville Longbottom could also be a main character, using his knowledge of plants to uncover secrets in the mansion's garden.