One possible fanfiction could be about Harry and Hermione teaming up secretly during the Triwizard Tournament tasks. They might use their combined knowledge and skills to outwit the other competitors. For example, in the maze task, they could have a special code to communicate and find their way to the Triwizard Cup faster than anyone else.
There might be a fanfic where during the Triwizard Tournament, Harry gets cursed and Hermione has to find a way to break the curse. She races against time, using every spell and potion she knows. Meanwhile, she also has to deal with the tournament tasks on Harry's behalf. In the end, through her determination and love for Harry, she manages to break the curse and they both complete the tournament in an unexpected way.
There are fanfictions where Hermione and Fleur become friends during the Triwizard Tournament. In some stories, they start to see past their initial rivalries. Fleur might initially see Hermione as just a book - smart girl, but as they face the challenges of the tournament together, they develop a mutual respect. Maybe they work together on the Yule Ball preparations within the context of the tournament, which helps to strengthen their bond.
One possible scenario in this fanfiction could be that Harry and Fleur form an unexpected alliance during the Triwizard Tournament tasks. They might discover they have complementary skills, like Harry's courage and Fleur's elegance and magic related to water (since she's from Beauxbatons). This alliance could lead to them facing the challenges in a new and interesting way, perhaps with Fleur using her Veela charm in a creative manner to distract the obstacles while Harry uses his Gryffindor bravery to take on the more physical parts of the tasks.
One great fanfiction could be where Harry and Luna team up in a unique way during the Triwizard Tournament tasks. Maybe Luna uses her off - beat magical knowledge to help Harry solve the puzzles in the maze. For example, she might recognize some magical creatures that Harry is unfamiliar with and guide him through.
One common plotline is that Hermione participates in the Triwizard Tournament instead of Cedric. This gives her and Harry a whole new dynamic as they face the challenges together. Another plotline could be that there's some sort of magical interference during the Tournament that makes Harry and Hermione realize their deeper feelings for each other. For example, a spell gone wrong that makes them share their innermost thoughts.
A plot twist could be that the Triwizard Cup is actually a portal to a different dimension, and Harry and Hermione accidentally get transported there during the final task. They then have to find a way back while dealing with strange creatures and magic in this new dimension.
Harry and Ron would be her most likely allies. They are her best friends, and even if they might be initially shocked or jealous of her being in the tournament, they would surely come around to support her. Another likely ally could be Cedric Diggory. He's a fair - minded and kind wizard, and he might see Hermione's intelligence and skills as an asset and offer to help or at least be friendly towards her.
One common plot is Hermione being an unexpected champion. Maybe she gets chosen by the Goblet of Fire due to some magical interference or a misunderstanding. Another plot could be her facing unique challenges during the tasks. For example, in some fanfictions, she uses her vast knowledge to outwit the challenges in a different way than the original champions. Also, there are often plots where Hermione has to deal with the jealousy and suspicion of her peers, since she's not supposed to be in the tournament in the first place.
In some fanfictions, the author might explore the idea that the person who dragged Harry into the Triwizard Tournament has a personal vendetta against him. Maybe it's a relative of a Death Eater who wants to see Harry fail publicly or even die during the tournament. Harry then has to not only survive the tasks but also figure out who is behind this plot against him.