Well, it could be used to change the course by revealing hidden spells or magic. For instance, if a character in the fanfiction discovers that the diary holds the key to a powerful protection spell that Voldemort (Tom Riddle) had created but never fully utilized. This spell could then be used to protect Hogwarts from a new threat that was not in the original story.
It could also change the story if the diary was used to create an unexpected alliance. Suppose a character finds the diary and instead of being afraid of it, they befriend the essence of Tom Riddle within. Riddle, for some reason (maybe the character offers something he wants), decides to help the good guys. This would completely change the course of the story as the most feared dark wizard's younger self is now on the side of the heroes, and they could use his knowledge and power to defeat other threats in the wizarding world.
In fanfiction, Tom Riddle's diary often serves as a key plot device. It can be a source of mystery and danger. Writers might explore how the diary manipulates those who interact with it, like Ginny in the original story. It can also be used to delve deeper into Tom Riddle's past and his early steps towards becoming Voldemort.
Tom Riddle's diary often plays a crucial role in fanfiction. It may hold secrets that were not explored in the original books. Fanfic writers might use it to introduce new magical concepts related to memory, possession, or the transfer of power. It can also create a sense of dread and anticipation as characters get closer to unlocking its true power.
In the original story, Harry often felt alone in his battles. But with an OC as his brother, there would be a constant ally. The OC could have different relationships with the teachers too. Suppose the OC has a particular interest in potions like Snape. This could lead to a different kind of mentorship and perhaps change Snape's view of the Potter family. And when it comes to the final battles, the OC could bring in additional magical artifacts or allies that were not part of the original story, completely changing the way the fight against Voldemort unfolds.
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.
If Harry isn't James's son in the fanfiction, it might lead to a different prophecy. In the original story, the prophecy was about Harry as the son of James and Lily. Without that relation, the prophecy could be about someone else entirely or have a different interpretation. Also, Voldemort might not target Harry in the same way. He targeted Harry because of the threat he posed as the son of James and Lily. This could lead to a very different power struggle in the wizarding world, with other characters coming to the forefront as the main targets or heroes.
In a scenario where they both travel to a different time period, say the Middle Ages, they could introduce new forms of magic or change the way magic is perceived. For example, if they introduce more advanced defensive spells during a time of great magical battles, it could change the balance of power between different magical factions. Their combined knowledge and influence could shape the development of magic in ways that would have a long - term impact on the history of magic, from the way spells are taught at Hogwarts to the political structure of the wizarding world.
Well, in fanfic, Tom Riddle's diary is significant as it represents a piece of Voldemort's past. It's like a window into his younger self, his thoughts and his early evil plans. It can be used to show how he started on his path to becoming the most feared dark wizard. For example, a fanfic might show how the diary records his first experiments with dark magic.
Tom Riddle's diary in fanfic can be a really interesting element. It can be portrayed as even more menacing. Some fanfics might show the diary having the ability to control more than just one person at a time. It could also be used to create a connection between different timelines. For example, a character from the present might be able to communicate with Tom Riddle from the past through the diary in ways that were not possible in the original story. This can lead to all sorts of new plot twists and character developments.
It would change the whole backstory of Harry. Instead of being an orphaned wizard with a connection to Voldemort, she'd have a connection to Loki. This would mean different motives and goals. Her character arc might not be about defeating Voldemort but rather about understanding her place in both the wizarding world and the Norse mythological world.
In this fanfiction, the prophecy about Harry and Voldemort might not hold the same significance. Since they are growing up together, the idea of one being the downfall of the other could be completely different. It could be that they end up working together to fight other dark forces in the wizarding world, rather than being enemies. This would rewrite a huge part of the original story's plot, which was centered around their enmity.