Another plot idea might be the characters dealing with the aftermath of the final battle in more depth. For example, they could be working on rebuilding Hogwarts and facing new challenges in the process, like dark magic remnants that are still causing trouble. They also might have to deal with some of the political unrest in the wizarding world that the war created.
One idea could be Harry and his friends exploring new magical realms that were previously unknown. Maybe they discover a hidden school of magic that has a different approach to teaching spells.
A great plot could be focusing on the love triangle between Harry, Ginny, and Hermione. Harry might struggle with his feelings for Ginny while also being really close to Hermione, and this could create some interesting drama and tension. Also, it could tie in with the events of the 6th year like the search for Voldemort's Horcruxes.
One idea could be to focus on Harry's relationship with Sirius Black in a more in - depth way. Maybe Harry discovers some hidden secrets about Sirius that even Sirius himself doesn't know yet. Another could be to create a new magical creature that is somehow related to the events of the third year, like a creature that is connected to the time - turner.
Well, a great plot for a Harry Potter third year fanfic could be centered around time - travel. Since Hermione has the Time - Turner in the third year, what if there was a glitch in it that sent some students back in time to the Marauders' era? They could interact with James, Sirius, Remus, and Peter, and this could change the course of events in the present. Also, a story where Harry starts to suspect that there is more to the Dementors than just being guards of Azkaban. He could start his own investigation, which would lead him to some dark secrets about the wizarding world's prison system.
One idea could be exploring Harry's training in magic during that summer. Maybe he discovers a new spell or a magical object that gives him an edge for the upcoming year at Hogwarts. Another could be focusing on his relationships, like his friendship with Ron and Hermione growing deeper as they secretly plan for the challenges ahead in Year 5. Or perhaps Harry uncovers a mystery in the wizarding world that is related to the events that will unfold in Year 5, such as a hidden connection to Voldemort's past actions.
Perhaps in the fanfiction, we could see a different side of the foreign students. Like, the Beauxbatons and Durmstrang students could have their own hidden agendas. One of them might be in love with Harry and tries to protect him during the tournament tasks. This would create a whole new dynamic of relationships and loyalties within the story.
Well, you could have a fanfic where Voldemort uses DND - style dark magic to open portals to other dimensions. The Order of the Phoenix has to quickly learn DND - style combat and magic rules to fight off the new threats that come through these portals. Harry could be sent on a special mission to find a DND - style mage who can teach them the counter - spells. Meanwhile, the Death Eaters are also trying to master this new form of magic for their own evil purposes. This would create a really exciting and unique story.
Perhaps a plot where the protagonist can choose to either side with the Ministry of Magic during a time of political unrest within the wizarding world or join a rebel group. This would involve different magical battles and moral dilemmas depending on the choice. In the 'harry potter cyoa fanfic', this could show different aspects of the wizarding society that we don't often see in the original books.
A cool plot for a Harry Potter Twilight fanfic could be a competition. The wizards from Harry Potter and the vampires and werewolves from Twilight compete in a series of challenges. These challenges could test both magic and the unique abilities of the Twilight characters. Or perhaps a love triangle between a Harry Potter character, a Twilight vampire, and a Twilight werewolf. It would be interesting to see how the different cultures and powers interact in matters of the heart.
Another plot could focus on the lives of the secondary characters from the original series. For example, Neville could be the head of Herbology at Hogwarts and discovers a new, dangerous plant that has some sort of connection to an ancient magic. The 'carry on fanfic' could then be about how he and his students deal with it, with some cameos from the main characters.
One idea could be that a dragon escapes from Gringotts and Harry has to use his skills to track it down. Maybe the dragon has a special connection to a powerful dark magic item that Voldemort was after.