Hermione might use her knowledge of magic to create distractions. She could perform spells that cause chaos among the Death Eaters, like a spell that makes their wands malfunction or creates illusions to confuse them. Then she could take the opportunity to escape while they are disoriented.
She could try to appeal to any sense of humanity or self - interest among the Death Eaters. There might be some who are not completely loyal or who might be swayed by the idea of a greater reward from the good side if they let her go. Hermione could try to negotiate with them, using her quick thinking and persuasive skills.
She could use her intelligence. Maybe she could pretend to cooperate while actually looking for loopholes in their plans or trying to send hidden signals to her friends. For example, she could subtly mislead them about the location of important items or people.
Hermione could resist the Death Eaters with her vast knowledge of magic. For example, she could use protective spells and charms she has learned from her studies. She might also use her quick thinking to outwit them in verbal exchanges, not giving them any information or advantage.
One consequence could be that she is forced to perform dark magic against her will. This would be a huge moral struggle for her, as Hermione is a firm believer in the light side of magic. It could also change her perception of herself and her magic abilities in a very negative way.
Well, in some fanfictions, Hermione might use her superior intellect. She could outwit the Death Eaters by setting up elaborate magical traps. For example, she could use transfiguration magic to create objects that suddenly turn into something dangerous when the Death Eaters approach. Another way could be through her extensive knowledge of potions. She might create a potion that incapacitates or kills them when they come into contact with it.
Well, in this kind of fanfiction, perhaps Hermione is captured because she was on a solo mission to retrieve some important magical item. The Death Eaters could use her knowledge to try and break into the secrets of the Order of Phoenix. Meanwhile, Hermione could be using her wits to delay them and send out hidden signals for help.
Well, she could end up in a duel with a powerful Death Eater. Hermione is a very skilled witch, so it would be a great show of her magical abilities. Maybe she discovers a new spell during the fight that helps her gain the upper hand.
Hermione's development would be a struggle between her true self and the persona she has to adopt. She would constantly be in a moral dilemma. On one hand, she wants to stay true to her values like friendship and justice. On the other hand, she has to pretend to support the Death Eaters' cruel ways. This internal conflict could lead to her becoming more introspective. She might start to question the very nature of good and evil, and through this journey, she could emerge as a more well - rounded and wiser character, ready to fight against the darkness in a more nuanced way.
If Hermione joined the Death Eaters in fanfiction, it would completely turn the original plot on its head. The Death Eaters are known for their dark magic and prejudice, which is the opposite of Hermione's values. This could lead to a very different kind of story, perhaps one where she tries to change the Death Eaters from the inside, or she could be a double agent. It would be a very dark and complex alternate universe.
One way it could develop is through the use of dark magic coercion. Maybe a powerful Death Eater discovers Hermione's intelligence and decides to use Imperius Curse to make her his slave. He could force her to use her magic skills for his evil purposes, like brewing dangerous potions or stealing valuable magical artifacts.
She could use her intelligence to outwit Voldemort. Maybe find a loophole in the security around her and make her escape.
They are popular because they put Hermione in a very challenging situation which tests her character. Fans like to see how their favorite characters react when pushed to the limits.