It could be that a new character who seemed friendly at first betrays Harry during his third year. For example, a new student who was actually a spy for the Death Eaters. This student might have gained Harry's trust by helping him with his schoolwork or by pretending to be on his side during Quidditch matches. Then, when the time was right, the student could expose Harry's hiding place of important magical items or his plans to protect Hogwarts.
Another idea is that a teacher who Harry trusted, like Professor Lupin in an unexpected turn of events, betrays him. Perhaps Lupin was forced by some dark force or blackmail to give away Harry's location to the bad guys. Lupin might have been threatened with something he held dear, like the safety of his werewolf friends, and had no choice but to betray Harry, which would be a heart - breaking betrayal for Harry who saw Lupin as a mentor.
One likely character could be Draco Malfoy. He's always been antagonistic towards Harry, and in the third year, he might find a new and more devious way to cause trouble for Harry. He could pretend to befriend Harry to get closer and then betray him by spreading false rumors or stealing something important from Harry.
Greyback might be trying to turn Harry into a werewolf. Since Harry is a very powerful wizard, if Greyback could succeed, it would create a werewolf with extraordinary magical abilities. This would be a very dark and dangerous plotline for a fanfic.
Maybe they were forced into it by some dark magic or a powerful dark wizard. They could have been blackmailed into betraying Harry to save their own lives or the lives of others they cared about.
One possible plot could be that Ash sacrifices himself to save Pikachu and his other Pokémon from a powerful, evil force. In the heat of battle, he realizes that the only way to stop the enemy from harming his beloved Pokémon is to give up his own life. His death then has a profound impact on the Pokémon world, with his friends and Pokémon left to carry on his legacy of kindness and determination.
Perhaps it's about an alternative form of magic that is discovered. This new magic could open up a third path where neither the dark side nor the traditional good side fully controls the future. For example, it could be a magic that focuses on balance and harmony, which changes the way everyone in the wizarding world views power and relationships.
Maybe Ichigo's death occurs due to a curse that he unknowingly activated. In the fanfic, this could lead to a whole new set of rules in the Bleach universe. His friends might then have to search for a way to break the curse and resurrect him. It could involve traveling to unknown realms or making deals with mysterious entities.
One possible plot could be that Hermione does something that Harry perceives as a great betrayal, like perhaps siding with the Ministry when Harry believes they are corrupt. This could lead to a deep - seated hatred from Harry.
Perhaps the fanfic could revolve around Harry Styles using 'camouflage' in a more metaphorical sense. For example, he could be trying to hide his insecurities or past traumas from the public eye. And as the story progresses, someone special might come into his life and gradually help him shed that 'camouflage' and face his real self.
One possible plot could be Harry using his magical skills for diplomatic relations within the wizarding government. He might be sent on missions to other magical countries to negotiate treaties or resolve disputes.
One possible plot could be that Harry is experimented on by dark wizards who are trying to create a new form of dark magic. They might use his unique magical abilities as a base for their experiments. Another could be that well - meaning but misguided witches and wizards experiment on Harry to find a cure for a deadly magical disease, thinking his famous resilience could hold the key. Or perhaps some alien - like magical creatures capture Harry and experiment on him to understand the human - wizard form better.