Maybe the twin goes back in time and has to deal with the differences in Hogwarts at that time. They could face challenges like different teaching methods and more strict rules, and their knowledge from the future helps them stand out in a unique way. They might also interact with young versions of beloved characters in unexpected ways, like helping a young Snape see a different side of magic.
A great plot could be that the twin accidentally changes something in the past that causes a rift in time. So they have to race against time to fix it while also trying not to disrupt the past too much. They might have to team up with a young Dumbledore or other important figures to set things right, all while hiding their true identity as a time - traveler from the future.
One idea could be that the twin discovers a hidden magic in the past that changes the course of wizarding history. For example, they might find a way to prevent a major dark wizard from rising before they gain too much power.
The twin could start off as a bit of an enigma to Hermione. Maybe they initially keep their identity as her twin a secret, and as they interact more in the past - Hogwarts setting, they gradually form a bond. They could start by sharing their love for books and knowledge, which is something Hermione values a great deal.
Well, a plot might be that Hermione is deaged due to a magical accident in the library. As a deaged Hermione, she has a different view on things. She might start to question the rules of Hogwarts more, as she doesn't have the same level of respect for them as her older self. Her friends, Harry and Ron, would have to deal with this new, more rebellious Hermione while also trying to figure out how to reverse the deaging spell. This could cause a lot of chaos in Hogwarts.
One plot idea could be Hermione helping Hagrid with a new magical creature he discovers. Maybe it's a creature that has unique abilities and Hermione uses her extensive knowledge from books to figure out how to take care of it.
One plot idea could be that Hermione, through some magical accident, ends up in the Asgardian realm. Thor then has to help her get back home while she uses her magic to solve various problems in Asgard, like dealing with a mysterious magical threat that the Asgardians' magic can't handle.
She could go back in time to the Triwizard Tournament and use her knowledge of future events to prevent Cedric's death. Maybe she figures out a way to expose Barty Crouch Jr. much earlier. Another plot idea is that Hermione travels back to the time when the Marauders were at Hogwarts. She could interact with them, and perhaps try to influence Sirius Black's fate, making sure he doesn't end up in Azkaban. She might also try to learn more about Remus Lupin's lycanthropy from a different perspective.
One plot idea could be that Hagrid discovers a magical lemon grove that has special properties. Hermione gets involved in researching it. They might face challenges like protecting the grove from dark wizards who want to use the lemons for evil potions. It could also involve them using the lemons' magic to help Hogwarts in some way, like curing a strange illness that has befallen some students.
One plot idea could be that Hermione discovers a long - lost spellbook of Salazar Slytherin. As she delves into it, she starts to understand his view of magic in a new way. Maybe the spells in the book are different from what she has learned before, and she has to struggle with whether to use them or not, given Slytherin's somewhat dark reputation.
A possible plot idea is that in an alternate universe, the wizarding world has different alliances. Hermione and Abraxas meet at a magical symposium where they are both presenting on different forms of magic. They initially clash but then realize they have more in common than they thought. Or perhaps there is a mystery that only their combined skills can solve. Maybe a dark magic artifact that is related to both Gryffindor and Slytherin, and they must put aside their differences to stop its power from being misused.
One plot idea could be that Hermione loses her sight due to a dark magic spell during a battle. She then has to rely on her other senses and her friends' help more than ever. For example, Harry and Ron could describe the magical texts to her so she can still study and find a way to reverse the spell. Another idea is that she's born blind in this fanfiction universe, but she still manages to excel at Hogwarts by using her extraordinary memory and auditory learning skills.
How about a story where Hermione discovers a hidden talent for transfiguration that even McGonagall is surprised by. They then work together to perfect this new form of transfiguration, but face opposition from some of the more traditional - minded professors. Or, in a post - war Hogwarts, they collaborate to reform the curriculum to include more practical and modern magic, all while dealing with the after - effects of the war on the students and the school.