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 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.
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.
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.
In some fanfictions within 'Harry Potter and the Legacy of Hogwarts', there could be a plot about time - travel. A group of students accidentally travel back in time and witness key events in Hogwarts' history. This could lead to them learning important lessons that they bring back to their own time. Or perhaps a plot where a new magical creature is discovered near Hogwarts and it has a special connection to the school's legacy. The students then have to protect the creature and in the process, learn more about the deep - seated magic that has been passed down through the generations at Hogwarts.
One interesting plotline could be Harry using his 'ownership' to reform the Hogwarts curriculum. He might introduce new classes like Muggle Studies for wizards to better understand the non - magical world. Another could be him using his influence to improve the living conditions for house - elves at Hogwarts, as he has always been sympathetic to their cause.
One interesting plotline could be Harry mastering new and powerful magic that was not explored in the original books. For example, he might discover a long - lost spellcasting technique. Another could be his relationships with other characters evolving in different ways, like a deeper friendship with Neville or a different kind of mentorship with McGonagall.
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.
One interesting plotline could be a magical adventure where Harry Potter and the Lady of Hogwarts team up to discover a long - lost secret within the castle. Maybe they find a hidden chamber that holds the key to an ancient magic that can save Hogwarts from a new dark threat.