Perhaps Hermione's transformation into a Death Eater is a result of a time - travel accident. She goes back in time, something goes wrong, and she ends up being influenced by the Death Eaters of that era. This would create a complex web of cause and effect in the fanfiction.
A great plot twist could be that the Death Eater she's betrothed to is actually a double agent himself. All along, Hermione thought she was the one with the upper hand in the undercover operation, but it turns out he's been playing a long - game too. This would completely change the power dynamic between them and add a whole new layer of complexity to their relationship.
One interesting plot could be Hermione being forced to work with a Death Eater undercover. This creates a lot of tension as she has to hide her true feelings and intentions. Another might be a story where a Death Eater has a change of heart because of Hermione's influence. It shows the power of her character. And then there could be a plot where Hermione discovers a hidden group of Death Eaters within Hogwarts and has to figure out how to expose them without getting caught herself.
One possible plot twist could be that the Death Eater she marries is secretly a double agent. He might be working against Voldemort from within the Death Eater ranks and Hermione discovers this. Their relationship could start as a way to get closer to the Death Eater secrets but then turn into real love.
Another plot twist might be a time - related one. What if John gets transported back in time to the events of the Harry Potter series and meets a younger Hermione? His different perspective and knowledge from his own world could change the course of events in the wizarding world, creating a complex web of changes and consequences.
In some fanfics, a plot twist could be that Severus was actually protecting Hermione all along under Dumbledore's secret orders, and Sirius discovers this and has to re - evaluate his hatred for Severus. This completely changes the dynamic between the three.
Well, it could be that Bellatrix adopts Hermione thinking she can use her to get to Harry Potter. But as time goes on, Hermione manages to turn the tables and uses Bellatrix's own desires against her. She convinces Bellatrix that she can lead her to greater power if she turns against Voldemort. This not only creates a rift between Bellatrix and her dark lord but also sets off a chain of events that no one could have predicted.
One interesting plot twist could be Hermione struggling with her dark heritage while trying to uphold her Gryffindor values. Maybe she discovers a hidden power within her that she initially fears is evil but later uses for good.
One potential plot twist could be that Hermione's father was actually a double agent. So, while everyone thinks she's the daughter of a Death Eater, in reality, he was working for the good side all along. Another twist might be that Hermione discovers she has some special powers because of her heritage that can be used to defeat Voldemort in a unique way. For example, she could have an innate understanding of dark magic that helps her counter the Death Eaters' spells.
Another aspect could be an unexpected bond forming between Hermione and the Death Eater. As they are forced to spend time together, they might start to understand each other on a deeper level. This could lead to a moral dilemma for the Death Eater, especially if he starts to develop feelings for Hermione. He would then have to choose between his loyalty to the Death Eaters and his new - found connection with her.
A possible plot twist could be that Hermione gets turned into a Death Eater against her will, and Draco has to help her break free from the dark magic controlling her. This would completely reverse their typical roles.