Bella's nightmares can also show her struggle with her new vampire identity. If she has a nightmare about not being able to control her thirst, it ties into her character's journey of self - discovery as a vampire. She was always a bit of an outsider as a human, and now as a vampire, she has new challenges to face. Carlisle's nightmares about his past sins are very much in line with his character. He is a morally upright vampire, constantly trying to atone for his past actions. These nightmares are a reminder of the internal conflict he has between his past and his present self, and how he is always striving to be better.
The Cullen family members are important characters too. Edward, for example, might have an interesting dynamic with Bella in this fanfiction. He could be either protective or jealous of Carlisle's special relationship with her.
There could be Edward. Even though the focus is on Carlisle and Bella, Edward's presence might still be felt as he was an important part of Bella's life before. His reactions to Carlisle and Bella's relationship could add some drama.
One idea could be Carlisle having to protect Bella from a new vampire threat that is specifically targeting her for her unique connection to the Cullens. Maybe a group of nomadic vampires who are jealous of the Cullens' lifestyle.
For Bella, a nightmare could involve her not being able to control her vampire instincts and accidentally harming someone she loves, like her father or one of her human friends. This would be a huge source of distress for her. Carlisle might have a nightmare where the Cullen family is ostracized by the vampire community for some reason, like breaking an important vampire law. He would be devastated as he has worked so hard to build a harmonious existence for his family within the vampire world.
Often, it starts with an unexpected encounter or a moment of realization. Maybe Carlisle sees Bella in a new light, not just as Edward's girlfriend but as an individual with her own charm. Then, there are small gestures of kindness and understanding between them that gradually build up the relationship.
They can also expand our view of their relationship. Fanfictions about nightmares might introduce new scenarios where their relationship is tested in ways not seen in the books. For example, a nightmare where Edward has to choose between Bella and his vampire family can show how complex their relationship is, as it involves different loyalties.
Well, of course, there's Dark Carlisle, who might be a character with a shadowy past and different moral compasses compared to the regular Carlisle. And then there's Bella. She is often portrayed as the one who tries to understand Dark Carlisle, bringing out different sides of him. There could also be other supporting characters from the Twilight universe, like the other members of the Cullen family, who might react differently to Dark Carlisle and Bella's relationship.
In some fanfictions, other members of the Cullen family can also be important secondary characters. For instance, Edward might play a significant role. He could be either a source of conflict, as he has his own feelings for Bella, or a mediator, trying to understand the strange attraction between Carlisle and Bella. Also, Esme, Carlisle's wife in the original story, could be a character that adds more complexity to the situation. Her reaction to Carlisle's feelings for Bella could range from heartbreak to acceptance, depending on how the author writes it.
One common theme is the exploration of Bella's fear of losing Edward. In the Twilight series, their relationship is intense, and in fanfictions about nightmares, this fear might be magnified. For example, she could dream that Edward leaves her for his vampire family's sake. Another theme is the danger that Edward's vampire nature poses in her nightmares. Maybe she dreams of him losing control and hurting her, which is a contrast to his usually protective nature in the original story.
It would likely shock and confuse many characters. For example, Edward would be very surprised and perhaps a bit jealous as he had a strong relationship with Bella. The Cullens as a family might be divided in their opinions. Some, like Esme, might be more accepting and try to understand, while others could be more hesitant. The werewolves would also be affected. They might see this as another strange and unpredictable aspect of the vampire world and it could potentially change their relationship with the Cullens. Jacob, in particular, would probably be very confused about Bella's new situation.