A third plot idea might be a fanfiction where the magical creatures of the Harry Potter universe take center stage. Maybe a story about how the centaurs, for instance, try to protect their forest from the encroachment of dark wizards. It could involve a young witch or wizard who befriends a centaur and together they fight against the forces of evil.
Another idea is a fanfiction that focuses on the Marauders' time at Hogwarts. We could see more of their pranks, their relationships, and how they dealt with the growing threat of Voldemort. For example, exploring how Sirius and Remus' friendship developed during those years in greater detail. It would also be cool to see more of James Potter's character before he became Harry's father.
One interesting plot could be if Harry was sorted into Slytherin instead of Gryffindor. It would completely change his relationships and how he's perceived. He might have to deal with the prejudices of his own house while also trying to figure out his role in the fight against Voldemort.
One idea could be a universe where Voldemort won the Battle of Hogwarts. The wizarding world would be in complete chaos and oppression. Harry could be in hiding, trying to find a way to fight back against Voldemort's regime. Another plot could be a world where the Sorting Hat makes different decisions for all the characters. For example, Hermione could be in Slytherin, which would completely change her relationships and the way she approaches magic. Or a parallel universe where magic is known to muggles and they co - exist in a very different way than in the original series.
One interesting plot idea could be a crossover where the 'across the universe' concept brings different magical universes from the Harry Potter world together. For example, the wizarding schools from different countries might interact in unexpected ways.
One plot idea could be that Lily's presence changes Harry's upbringing completely. Instead of growing up with the Dursleys, he has a loving home with his mother. Maybe she starts teaching him magic early on, which gives him an edge when he enters Hogwarts. This could also lead to a different dynamic with his friends, as he might be more confident and skilled from the start.
One idea could be a crossover with the Lord of the Rings universe. Harry and his friends could find themselves in Middle - earth, having to deal with Sauron's forces while also using their magic. Another could be a crossover with the Star Wars galaxy, where wizards and witches interact with Jedi and Sith. Maybe they could learn from each other's use of the Force and magic.
One idea could be that in this alternate universe, Hufflepuff is the dominant house in Hogwarts. They have a secret society within the house that holds the key to an ancient magic that can save the wizarding world from a new, unknown threat. And the main character, a Hufflepuff student, discovers this by accident and has to take on the responsibility to gather the members of the society.
A great plot for a Potter Manor fanfiction could involve a mystery that surrounds the manor. For instance, strange noises at night lead Harry to uncover a long - forgotten chamber. It could also be about Harry restoring the manor to its former glory, perhaps with the help of Hermione's research on ancient magic used in the construction of such manors.
A traveler could be from a different magical realm entirely and come to the Harry Potter universe. They bring with them unique magical abilities that both fascinate and frighten the wizards in the Harry Potter world. This could lead to a series of adventures where they either share their knowledge or are hunted down by those who fear the new magic they possess.
One idea could be that Hecate, being the goddess of magic, takes Harry Potter under her wing secretly to teach him ancient and powerful magic that Dumbledore doesn't know. This could lead to Harry having new abilities to fight Voldemort.
A possible plot in Harry Potter Planeswalker fanfiction is that a Planeswalker accidentally brings a dangerous creature from another plane into the Hogwarts grounds. This causes chaos as the teachers and students have to figure out how to deal with it. It could also be that a Planeswalker has a special connection to the magic in the Harry Potter world, like being able to sense the presence of magic in a way that wizards can't. They could use this ability to discover hidden secrets about Hogwarts or the wizarding families. Maybe a Planeswalker is on a quest in the multiverse and the Harry Potter world is just one stop on their journey, and their actions in the wizarding world have consequences for their overall mission.