What are some interesting plotlines in 'Harry Potter the Fourth Year fanfiction'?

A possible plotline is that in their fourth year, there is a new student who seems to be a threat to Harry. Hermione suspects that this student has some connection to the Death Eaters. She and Harry start to investigate. Along the way, they face many challenges and misunderstandings. But through it all, they learn to trust each other more and their friendship blossoms into something more as they work to protect Hogwarts from this potential threat.

A really badass plotline could be Harry having to face a much more dangerous and complex version of the maze in the Triwizard Tournament. Instead of just physical obstacles, there are magical creatures from different realms and dark magic traps. Harry has to use all his skills and knowledge, including some that he's picked up from his interactions with Sirius and Lupin, to make it through the maze alive.

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 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 secretly learning advanced magic on his own to better prepare for the coming battles. He might discover an old, forgotten spellbook in the Room of Requirement.

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.

One interesting plotline could be an alternate take on Sirius Black's escape. Maybe in the fanfiction, he has some secret magical help that wasn't in the original story. Another could be a story where Harry discovers a new spell during his third year that changes the way he deals with the Dementors. For example, instead of using the Patronus charm right away, he finds a spell that temporarily disables the Dementors' ability to sense fear.

One interesting plotline could be Harry's further exploration of his connection with Voldemort. Maybe he discovers new magical abilities within himself as a result of this connection. Another could be the relationships between the characters evolving in unexpected ways. For example, Neville could take on a more prominent leadership role among the students.

Well, in some 'Harry Potter Year Eight Fanfiction', a plotline might involve the rebuilding of Hogwarts after the war. Harry could play a crucial role in this, using his influence and experience. Also, there could be a story about the integration of Muggle - borns and pure - bloods in a more harmonious way, with Harry leading the charge for equality. There might also be a mystery surrounding some dark magic that still lingers from the war.