The character could be introduced as a new neighbor to one of the main characters. Let's say a 31 - year - old witch moves in next to Harry. She is mysterious at first, but as the story unfolds, we learn that she has a special connection to an old dark magic incident that Harry and his friends are currently investigating. This way, she becomes an integral part of the story gradually.
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.
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 Harry Potter fanfiction, 'the year of darkness' could refer to a period of great turmoil, perhaps a year when Voldemort's forces are at their strongest, or when some other dark magic is prevalent. It might be a time when the wizarding world is on the verge of collapse and the characters face extreme challenges.
Make sure the character's actions are consistent with their personality. If they are shy, they won't suddenly be the center of attention in the Great Hall without a good reason. Their growth throughout the fanfiction should also be gradual. In the fourth year at Hogwarts, there are a lot of new challenges like the Triwizard Tournament. So, the character should respond to these challenges in a way that is in line with who they are.
A really engaging one is 'Year Four Revelations'. In this fanfic, the author explores the relationships between the characters during Harry's fourth year. It shows a different side of how the students interact and deal with the events of that year. There are some great character - building moments and it's very immersive.
A great Year 4 Harry Potter fanfiction often stays true to the essence of the original story. It should have the main characters like Harry, Ron, and Hermione behaving in a way that is consistent with their personalities in the books. For example, Harry's bravery and Hermione's intelligence should be prominent.
In AU 4th - year fanfictions, relationships can change a great deal. For example, if Harry was raised by Sirius instead of the Dursleys. His confidence might be higher, and his relationship with Draco could be less antagonistic from the start. Maybe they could even become reluctant allies in the face of a new threat at Hogwarts. Also, Hermione might form a closer bond with Neville as they study together more often in this AU, and Ron could become a bit jealous of their newfound friendship.
Another plot could revolve around Harry's Occlumency lessons. In fanfiction, it could be that instead of just trying to block his mind from Voldemort, he actually manages to use Occlumency to his advantage. He could start to plant false thoughts in Voldemort's mind through their connection, leading Voldemort astray in his plans.