Another theme is the struggle between the vampire and human worlds. Caius, being a vampire, is often in the middle of this conflict in fanfiction. Some stories might show him trying to find a balance between the two worlds, while others might have him firmly on the side of the vampires and fighting against human interference.
Love is also a prevalent theme. Caius, despite his tough exterior, is often given a love interest in fanfiction. This could be a human or another vampire, and it usually changes his character in some way. It might make him more empathetic or more protective.
One common theme is power. Caius is a powerful character, and many fanfictions explore how he wields his power, whether it's for good or bad. For example, some stories might show him using his power to protect the vampire coven.
One common theme is the struggle between different vampire clans. Since Caius is part of the Volturi and Bella has her own connections, this often creates a backdrop of power struggles and politics in the fanfiction.
One common theme is the struggle against the odds. Since their relationship might not be accepted easily in the vampire world, they often have to fight for their love.
Many of these fanfictions explore the theme of identity. Harry has his own identity as a wizard, and Caius has his as a vampire. When they become mates, they have to reconcile their identities and find a new combined identity. This exploration of identity makes the stories really interesting.
Power dynamics is another theme. Caius has a certain power, and the OC may or may not have their own powers. The fanfictions explore how these power levels interact and how they influence the relationship, whether it's through protection or a power struggle.
One common theme is the struggle against the odds. Since Bella and Caius are from different 'worlds' in a sense, they often have to face opposition from other vampires or even Bella's human friends. Another theme is the discovery of a deep, new connection. It's about how they come to realize their bond as mates.
Love against all odds is also a big theme. Caius is part of the Volturi, which makes their relationship controversial. But in many fanfictions, their love overcomes these obstacles. They find a way to be together despite the expectations and rules of the vampire society.
Another theme is redemption. Caius, being a somewhat villainous character in the original, is sometimes given a chance at redemption through his relationship with Lightning. It gives a new perspective on his character. For instance, in some stories, Lightning's unwavering sense of justice makes Caius re - evaluate his own actions.
One common theme is identity. Bella has to re - define who she is as Caius' sister instead of just being Edward's love interest. Another theme is family loyalty. She has to figure out where her loyalties lie between the Cullens and the Volturi.
The themes of transformation and self - discovery are quite common. Bella's transformation into a vampire (if it occurs in the fanfic) and how that affects her relationship with Caius is often explored. Caius, too, may go through a form of self - discovery as he gets involved with Bella. Another theme is the struggle against fate. Their relationship is often seen as something that is not meant to be according to the rules of their world, but they fight against that in the fanfiction.
One common theme could be friendship. How they interact as friends and support each other. Another might be adventure, like going on quests together.