Perhaps Harry is teaching Potions in the fanfiction. Since he had a bit of a rocky start with Potions in his student days, he could be a very understanding teacher. He might encourage students to experiment more, which is different from Snape's strict methods. He could also share stories about how important Potions were in his adventures, like when they made Polyjuice Potion. This would make the class more interesting and inspire students to take Potions more seriously.
Perhaps the story could revolve around them facing challenges within the Hogwarts faculty. There could be some old - fashioned professors who oppose their modern teaching methods. Harry and Hermione then have to prove that their ways are beneficial for the students. They might also discover new magical abilities in some of the students that were previously overlooked, and help those students develop their skills.
Well, perhaps Harry Dresden could introduce his unique brand of magic from his own world into Hogwarts. He might teach the students new ways of dealing with magical creatures that are different from the traditional Hogwarts methods.
Well, perhaps Percy could be teaching a new and difficult subject like Ancient Runes. He might use his strict and studious nature to get the students to really focus on the complex rune translations.
Hermione would surely be a main character. She could be a fellow teacher, perhaps teaching Transfiguration or History of Magic. She would be the one Harry goes to for advice on teaching methods or when he has a difficult student. Another character could be Ron. He might visit Harry at Hogwarts and end up getting involved in some of the school's mysteries or helping Harry with a particularly difficult Quidditch - loving student.
Maybe Harry Potter could teach the preschoolers magic tricks in a simple and safe way, like making feathers float. He could also tell them stories about Hogwarts and his adventures, inspiring their imagination.
One possibility is that Merlin brings his ancient magic knowledge. He might introduce spells and magical concepts long forgotten in the Hogwarts curriculum. For example, he could teach students about pre - Hogwarts era potion - making techniques that are more in tune with nature.
One possible plot could be that Harry, using his knowledge of love and friendship, tries to teach Tom about the power of positive emotions. He might show Tom how his own journey was shaped by the love of his friends and family, in contrast to Tom's more solitary and power - hungry path. Maybe Harry takes Tom to Hogwarts in a time - travel like scenario and shows him the true meaning of the houses, not just the pursuit of power within Slytherin.
Well, it could be about Harry facing an even greater threat than Voldemort. Maybe a new dark wizard emerges from the shadows and Harry has to use all his skills and the support of his friends to defend Hogwarts as its champion. He might have to go through a series of super - difficult challenges that test his magic, courage and loyalty to an extreme level.
One possible plot could be that Harry Potter, as the new owner of Hogwarts, decides to reform the school's curriculum. He might introduce new magic subjects that were previously overlooked, like ancient rune magic for practical applications.
Well, it could be about Harry's journey to fully embrace his role as a prince in Hogwarts. Maybe he discovers some long - lost royal heritage of the wizarding world that gives him new powers and responsibilities.