A great plotline might involve the relationships between the students in more depth. For example, how Hermione and Ron's relationship evolves during this year with new challenges and tensions added. It could also show Harry's struggle with his feelings for Ginny in a more detailed and unique way compared to the original book. Some fanfictions might also focus on the mystery of the Half - Blood Prince's identity and how it affects the Hogwarts community in different ways than what was shown in the official story.
Some fanfictions could center around the introduction of new spells and magical concepts that were only hinted at in the 6th year. This could include a deeper exploration of the potions class under Slughorn, like the discovery of rare ingredients and their uses. There could also be a plotline where a student discovers a hidden talent for a particular type of magic that is related to the events of the 6th year, such as a new form of defensive magic against the Dark Arts that Voldemort might be using.
One interesting plotline could be exploring more of Snape's inner turmoil during Harry's 6th year. Maybe showing his secret efforts to protect Harry while still maintaining his cover among the Death Eaters.
One interesting plotline could be Harry's struggle with his new role as a leader in Dumbledore's Army. He has to deal with the pressure of teaching his peers and also keeping the group a secret from Umbridge.
One interesting plotline could be Harry dealing with the aftermath of the war in Hogwarts. He might be trying to heal the school and its students from the trauma. Another could be his relationship with Ginny evolving further as they face new challenges together in their final year.
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.
One interesting plotline could be a deeper exploration of the Triwizard Tournament tasks from a different perspective. Maybe showing the behind - the - scenes preparations by the champions that we didn't see in the original book. Another could be a new relationship developing between characters, like a friendship between a Hogwarts student and a Durmstrang student that impacts the events of the tournament.
In many Harry Potter 8th year fanfic plotlines, the exploration of the wizarding world outside of Hogwarts becomes a major focus. Harry and his friends could be traveling to different wizarding communities, learning about their cultures and magic. They might encounter new magical creatures and have to figure out how to interact with them. There could also be a mystery involving a powerful, ancient magic that is somehow related to their 8th year at Hogwarts, and they have to solve it to keep the wizarding world safe.
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.
In some fanfictions, there could be a plotline where Harry and Hermione start to realize their feelings for each other in a different way during their 6th year. They've been through so much together, and this year could be the turning point where their relationship evolves from just friendship. They might have more private moments, sharing their fears and hopes, and this newfound closeness could lead to a whole new dynamic in their relationship.
In some fanfiction, there are plotlines where the Death Eaters have a different strategy. Instead of just following Voldemort blindly, they start to have their own power plays. This could lead to a more complex battle between the good and the bad. Also, there could be a plot where Harry has to deal with a new magical ability that he discovers during year 7, which changes the whole dynamic of the fight against Voldemort.
One could be a 31 - year - old Harry looking back on his Hogwarts days and realizing how much he has grown. He might be mentoring young wizards and witches, passing on the knowledge and skills he learned. For example, he could be teaching them how to face dark magic threats, using his own experiences as a guide.
A common plotline is the deepening of relationships. For example, Harry might further develop his friendship with Draco. They could start to understand each other better, realizing that they were both products of their upbringing. Also, Hermione could take on more leadership roles in the school, like starting new study groups or magical research projects, which would be really exciting to read about in fanfiction.