It could also be a new generation of students. For instance, the children of the original characters. They might go on a field trip to explore an ancient wizarding ruin. During the trip, they discover secrets about their parents' time at Hogwarts and how it relates to the ruin they are exploring. This would add a new dimension to the Harry Potter universe in the fanfiction.
In fanfiction, during a Harry Potter field trip, students might encounter new magical creatures not in the original books. For example, they could come across a herd of rainbow - colored unicorns in a hidden glade. They may also visit a wizarding village that was never mentioned in the main series and learn unique spells from the local wizards there.
The main characters are Gohan and Videl, of course. Gohan is a half - Saiyan with great power, and Videl is a strong - willed martial artist.
Peter, of course, is the main character. His classmates could also be important characters. Maybe there's a nerdy kid who helps Peter solve problems during the trip. The teacher in charge of the field trip is also likely to be a character. There could be a local guide at the field trip destination who has some interesting stories to tell.
It could be a rival company's spy. They want to steal Stark Industries' secrets during the field trip. Maybe they disguise themselves as a tour guide or an intern to get close to the valuable information.
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 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.
Even Neville Longbottom's descendants could be interesting main characters. Maybe his grandson has a unique talent for herbology, like Neville did. He could use his skills to uncover a plot that involves poisoned plants in the Hogwarts gardens and throughout the wizarding world, and along the way, he becomes a hero in his own right.