In 4th - year Harry Potter fanfics, a popular plot is Harry's training for the Triwizard tasks. He could be getting secret help from an unexpected source, like a former champion or a hidden teacher at Hogwarts. His relationship with Cedric Diggory can also be a major part of the story. It might start as a rivalry but develop into a mutual respect. Plus, the way the fanfic portrays the magic in the tasks, like the underwater scene in the second task, can be really interesting and unique to each writer.
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 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 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 common plotline could be a friend turning against Harry due to jealousy. For example, Ron might be jealous of Harry's fame and betray him by revealing his secrets to the Death Eaters. Another could be a teacher who was thought to be trustworthy, like Snape in a different scenario, actually working against Harry all along. Or perhaps a new character introduced in the fanfic who befriends Harry only to betray him for some dark magic - related motives.
Well, he might be able to change some of the bad things that happened. Maybe he could stop Umbridge from being so cruel. He could also be better prepared for the challenges that year brought, like the fight against Voldemort's forces.
One interesting plot could be about Harry forming an unexpected alliance with some Slytherin students during his 5th year. They might team up to uncover a mystery within Hogwarts that involves a dark magic item that was planted there by Death Eaters. This could lead to a lot of character development as they learn to trust each other despite their house differences.
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.