The drugged sister's character could also develop in terms of her understanding of the supernatural world. At first, she might be completely in the dark about how the vampire world works. But as the drug affects her and she has various encounters with vampires, she could start to piece together the rules and politics of the vampire society. This new knowledge could make her more confident and assertive, and she could even start to challenge the vampires on their own turf, using her wits and the strange powers or insights the drug has given her.
Her character could be developed through her relationships with other characters in the Vampire Diaries universe. If she's drugged, she might be more open to forming unexpected alliances. For instance, she could form a bond with a vampire who initially intended to harm her but then changes his mind. Through this relationship, she could learn about the vampire's past and in turn, it could shape her into a more empathetic and understanding person, despite her drugged and confused state.
The drugged sister could start off as a very vulnerable character. But as the story progresses, she could develop a sort of inner strength. For example, she might initially be terrified of the vampires and the strange things she's experiencing due to the drug. But then, she could learn to use the drug - induced changes in her perception to her advantage, like being able to sense when a vampire is near even before they show up.
One plot idea could be that the sister, after being drugged, has some sort of psychic connection with the vampires in The Vampire Diaries world. Maybe she can see their memories or feel their emotions, which leads to a series of adventures where she tries to use this new - found connection to help or hinder the vampires' actions.
The OC sister can be developed by showing her initial naivete. For example, at the start, she trusts her siblings completely. Then, when the betrayal occurs, her personality could shift to become more cynical. We can see her grow by having her learn new skills like self - defense or magic in order to protect herself from her siblings.
One common theme is the struggle for self - identity. Since the sister is compelled, she often has to fight against the actions she's forced to do and figure out who she really is outside of the compulsion.
There's a fanfiction titled 'Sister's Compulsion: A Vampire Diaries Tale'. In this one, the sister character is compelled to do various things that have far - reaching consequences in the world of Mystic Falls. The author does a great job of staying true to the feel of the Vampire Diaries while adding their own unique twists.
An OFC could be related to chloroform if she's a doctor or a healer in the fanfiction world. She might use chloroform in her medical practice, perhaps on a vampire who is injured and needs treatment but is also a danger due to their vampire nature. So, chloroform could be a tool to keep them under control during treatment.
You can also explore the impact on the relationships within the Vampire Diaries universe. Maybe the sister was in a relationship before the amnesia. Now, her partner has to deal with her not remembering their love. It could lead to some really interesting plot twists, like the partner having to fall in love with her all over again while she discovers new aspects of herself.
In some fanfictions, Elena's autistic sister might be portrayed as having unique sensitivities. For example, she could be highly sensitive to sounds or lights, which might play a role in the Vampire Diaries' supernatural setting. Maybe she has a special connection to the vampires or other supernatural beings because of her different way of perceiving the world.
One common theme is loyalty. Sisters in the fanfiction often show unwavering loyalty to each other despite the supernatural challenges they face. Another is sacrifice. They might be willing to sacrifice their own happiness or safety for their sister. For example, in many stories, a sister will put herself in danger to protect her sibling from a vampire or a witch's curse.
In Vampire Diaries fanfiction, the concept of a twin sister sacrifice can add a whole new layer of drama. It could be related to some dark magic ritual where a twin's sacrifice is needed to gain power or break a curse. For example, perhaps a powerful vampire or witch demands it to achieve immortality or to control the supernatural elements in Mystic Falls.
One common theme is family loyalty. The sisters often have to stick together in the face of the many threats in the vampire - filled world. Another is power struggles. The sisters may have unique powers that others want to control or use for their own gains.