One great fanfiction idea could be Harry dealing with the Triwizard Tournament challenges in unique ways. Maybe he discovers a hidden power within himself that helps him out during the tasks, like a new form of magic he didn't know he had.
A possible plotline could be that Hogwarts itself becomes a sort of magical battleground earlier than expected. The Death Eaters try to take over the school completely, and the students and remaining teachers have to fight back in a sort of guerilla warfare within the castle walls. This would change the whole dynamic of the seventh year, with classes being interrupted and students having to use their magic in real - life combat situations.
A plot could be that Harry has premonitions about the Triwizard Tournament tasks before they happen. These premonitions are not clear at first, but as he gets closer to each task, he starts to understand them better. It adds an element of mystery and foreshadowing to the story.
Another interesting plot could be that Harry's connection to Voldemort causes some strange magical disruptions during the Triwizard Tournament. These disruptions seem like accidents at first, but Harry gradually realizes they are being caused by his own dark - side related powers that are being awakened in his fourth year.
Make sure the character's actions are consistent with their personality. If they are shy, they won't suddenly be the center of attention in the Great Hall without a good reason. Their growth throughout the fanfiction should also be gradual. In the fourth year at Hogwarts, there are a lot of new challenges like the Triwizard Tournament. So, the character should respond to these challenges in a way that is in line with who they are.
Another important character could be a new student or a transfer student. This character could bring in a fresh perspective and perhaps be a link to the new threat or mystery in the story. The Headmaster or Headmistress, whether it's Dumbledore (if he's still alive in this fanfiction) or someone else, would also be very important as they are responsible for the safety and well - being of the students during Harry's last year at Hogwarts.
Perhaps in this fanfiction, the plot focuses on Harry's relationships during his last year. He could be trying to mend some broken friendships or develop new ones. There might also be a romantic sub - plot where Harry finally figures out his true feelings for Ginny and they face some challenges together. Meanwhile, there could be a mystery surrounding an old Hogwarts secret that is uncovered during their last year, leading to an adventure that involves all the students.
In the fanfiction world, Harry might be the heir to Hogwarts if there was some sort of magical pact made generations ago. For example, perhaps one of his ancestors had a special role in the creation or protection of Hogwarts, and this role was passed down through the family. It could also be that his unique magical abilities, like his ability to resist Voldemort's attacks from a young age, are signs of a deeper connection to Hogwarts itself. This connection could be what designates him as the heir in the fanfiction's plot.
The mystery surrounding Voldemort's return is also a common theme. Fanfictions often explore how the students and teachers at Hogwarts start to suspect and then deal with the news. Additionally, the theme of identity is prevalent. Harry is constantly trying to figure out his place in the wizarding world, especially with all the new attention from the tournament and the rumors about him and Voldemort.