Another plot idea is that the diary gets into the hands of a student who is being bullied. The diary starts to give this student advice on how to get revenge. However, as the student follows the diary's suggestions, they slowly start to lose their own identity and become more like Tom Riddle. Eventually, their friends notice the change and must figure out a way to break the diary's hold on them before it's too late.
A possible plot could involve the diary being used by a group of students who want to learn more about the history of Hogwarts. They start to communicate with the memory of Tom Riddle within the diary, but soon realize that there are dangerous powers at play. As they delve deeper, they must find a way to stop the diary from influencing them too much and causing chaos in the school. For example, they might notice that the diary is starting to make them act more like Tom Riddle in his more malevolent moments.
Another plot could involve the diary having some sort of connection to the other Horcruxes. The protagonist, using their knowledge from the Harry Potter series, tries to use the diary to find the other Horcruxes. This would be a really exciting adventure as they navigate through the dark magic associated with both the diary and the Horcruxes.
One idea could be a time - travel fanfic where Harry goes back in time and tries to prevent Tom Riddle from becoming Voldemort. He could try to befriend the young Tom and show him a different path. Another could be a fanfic where Harry and Tom are somehow trapped in an alternate dimension together and have to work together to escape, all while Harry tries to understand what made Tom turn so evil. A third idea is a fanfic where Tom Riddle actually has a change of heart early on due to some magical accident that makes him experience a different kind of love and kindness, and Harry has to deal with this new Tom in Hogwarts.
A great idea for a Harry Potter diary fanfiction is to set it in an alternate universe. In this universe, the diary was never used by Voldemort. Instead, it's a tool for a young Gryffindor student who's having trouble with schoolwork. The diary becomes a sort of magical tutor, giving the student advice on how to improve their spells and potions. But as the story progresses, they start to notice strange things about the diary, like it seems to know things it shouldn't. This could lead to a mystery within the story.
One plot idea could be a time - travel scenario where Harry goes back in time and meets a young Tom Riddle. He tries to change Tom's path to prevent him from becoming Voldemort. Another could be a situation where they are magically bound together and have to learn to co - exist and understand each other's motives.
One plot idea could be a time - travel fanfic where Harry Potter goes back in time and tries to prevent Tom Riddle from becoming Voldemort. He could attempt to befriend the young Riddle and guide him towards a different path, perhaps by showing him the value of love and friendship early on.
One idea could be that Harry discovers a time - traveling device and goes back to Tom Riddle's childhood. He decides to take Tom under his wing and raise him with love and kindness. As a result, Tom doesn't become Voldemort and instead uses his magical abilities for good.
In a 'Harry Potter meets Tom Riddle' fanfiction, a really unique plot could be that Tom Riddle is reborn as a normal wizard without the dark desires due to some powerful magic. Harry Potter meets this new Tom and they become friends at Hogwarts. However, there are still some remnants of the old Tom's power that attract dark forces. So, Harry and Tom have to work together to fend off these threats while also exploring Tom's new identity and how it affects the future of the wizarding world. This would involve a lot of character development for both Harry and Tom, as they navigate their relationship in this new scenario.
One idea could be a time - travel plot where Harry goes back in time and tries to prevent Tom Riddle from becoming Voldemort. He could try to befriend the young Tom and show him a different path. Another could be a scenario where they are both put in a magically created alternate reality where they have to work together to escape.
Perhaps the locket contains a part of Tom's soul that is still somewhat 'good'. Harry accidentally releases this part while investigating the locket. This 'good' part of Tom then tries to help Harry defeat the remaining evil parts of Voldemort, leading to a very strange alliance between Harry and this new aspect of Tom.
One idea could be that in this fanfiction world, because of the physical resemblance, Harry is often mistaken for a descendant of Tom Riddle in a more positive light than in the original series. This could lead to some witches and wizards believing he has the potential for great power without the dark taint. For example, he might be offered special training by some old wizarding families who want to use his supposed connection to Riddle for good. Another plot could involve Harry using this resemblance to infiltrate a group of Death Eaters who are trying to revive Voldemort in a new way. He could pretend to be on their side, learn their secrets, and then expose them.