A more complex plot could involve Hermione being transported back in time to a period when the Death Eaters were more prominent. There, she has to interact with a Death Eater who is different from the others, perhaps more morally ambiguous. They end up influencing each other's views on magic and the wizarding world. This kind of time - travel plot combined with the Hermione - Death Eater dynamic can lead to a very engaging and rare fanfiction.
One idea could be Hermione discovers she has a long - lost pureblood heritage that has some ties to the Death Eaters. Maybe her family was involved in some secret Death Eater plot in the past, and she has to uncover the truth to clear her family name.
One idea could be that Draco and Hermione are forced to work together undercover among the Death Eaters. They start off distrusting each other but as they face various challenges within the Death Eater ranks, they begin to understand each other better. For example, they might have to find a way to stop a particularly heinous Death Eater plan while pretending to be on their side.
One plot idea could be a werewolf Death Eater who is forced to work with Hermione under some strange circumstances. Maybe they are both on a mission to retrieve a powerful magical artifact, and along the way, the werewolf starts to question his loyalty to the Death Eaters as Hermione shows him the value of kindness and justice.
One possible plot idea could be Hermione using her intelligence to outwit the Death Eaters in a mind - game. For example, she might pretend to be on their side while secretly working against them to save her friends. Another could be a scenario where she has a strange connection or shared past with a particular Death Eater that she discovers during a dangerous encounter.
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.
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.
Well, often there's a theme of power struggle. The Death Eater has certain powers and beliefs that might clash with Hermione's. But through their relationship, they might find a balance. Another common theme is the exploration of the grey area between good and evil. Just because the character is a Death Eater doesn't mean he's all bad, and Hermione might start to see that. And of course, there's the theme of trust - can Hermione really trust this Death Eater, and how does that develop over the story?
Often, they start with Hermione being in a vulnerable situation, like being captured by Death Eaters. Then, the plot may develop as she tries to resist their demands. For example, she might use her knowledge of magic to find a way out.
One common plot twist is that Hermione was actually a double agent all along. She pretends to be a Death Eater spy but is really gathering information for the Order of the Phoenix. This adds an element of mystery and excitement as the other characters in the story are initially unaware of her true motives.
Bellatrix Lestrange is also a likely candidate. Her encounter with Hermione would be extremely intense. Given her loyalty to Voldemort and her rather unhinged nature, she would likely pose a serious threat to Hermione, but Hermione might also find a way to use Bellatrix's madness against her.