In some fanfictions, they could be practicing to fight against the Dark forces that are starting to rise again. Hermione is researching ancient spells and Harry is trying to master them in order to be better equipped to face Voldemort or his followers once more. This would involve a lot of intense training sessions and a deepening of their friendship as they rely on each other more.
One possible plotline could be that they are practicing magic for an upcoming difficult exam at Hogwarts. They might be working on advanced spells like the Patronus charm and Hermione is helping Harry perfect it.
Maybe they are practicing for a wizarding duel competition. Hermione is using her vast knowledge of spells and Harry is using his natural talent and they are learning from each other. They could be facing off against tough opponents like Draco and his cronies in the competition, so they need to be well - practiced.
In some fanfictions, their training might involve time - traveling. Maybe they go back in time to learn from the founders of Hogwarts. Harry could learn how to better control his connection to Voldemort through this time - traveling training, and Hermione could study ancient magic from the founders. This would add a whole new dimension to their skills and knowledge.
One possible plotline could be Hermione using her intelligence to create a stable and loving home environment for Harry. Maybe she helps him deal with his PTSD from his past traumas. Another could be them facing magical threats together as a family, with Hermione teaching Harry new spells and ways to protect himself.
One interesting plotline could be Harry and Hermione discovering a long - lost secret vault in Gringotts. Maybe it contains powerful magical artifacts that can change the course of the wizarding war. Another could be that they are on a mission to retrieve something from the vault that is crucial for their fight against Voldemort, like a spellbook with ancient and powerful spells.
One possible plotline could be that they escape from a dark wizard's lair. Maybe they use their combined magic skills and Hermione's extensive knowledge to find a secret passage out. Another could be escaping from a dangerous magical creature's territory by using clever spells and potions.
Perhaps a plot where they all become animagi and have to use their animal forms to solve a mystery in the Forbidden Forest. Draco as a sleek snake, Harry as a stag, and Hermione as an otter, they must navigate the forest's dangers and uncover the truth about a strange magical disturbance.
A plotline could involve the relationship between Harry, Hermione, and their friends in the context of having twins. Their friends like Ron and Ginny could be very involved in the twins' lives. Ron might be the fun uncle who always brings the kids interesting magical gadgets, and Ginny could be the aunt who teaches them Quidditch. Also, the twins' education at Hogwarts could be a major plotline. They might face different challenges compared to other students due to their parents' fame.
One interesting plotline could be Harry's struggle with his newfound dark power while Hermione tries to bring him back to the light. For example, Hermione might use her vast knowledge of magic to find ancient spells that could reverse the dark influence on Harry. Another plotline could involve them facing off against their former friends who are now afraid of Harry's transformation. This would create a lot of tension and conflict in the story.
One interesting plotline could be Harry and Hermione learning different parenting styles in the class. For example, they might study how to handle a child's magic outbursts, which is a very unique situation in the wizarding world.
Maybe in this fanfiction, the fact that they are the Riddle Twins causes a stir in the wizarding community. Some people might fear them because of their connection to Voldemort, while others believe they could be the key to finally bringing true peace. Harry and Hermione then have to deal with the prejudice and the high expectations placed on them. They might have to prove that they are not like Voldemort and that their heritage can be used for good.
One interesting plotline could be how they navigate their new relationship while still dealing with the threats in the wizarding world. They might have to balance their duties as friends to Ron and their new marital status.