Well, it could be about Bella being in a role where she is like a mother figure to the Volturi in a fictional scenario. Maybe it involves her having some sort of special relationship with them, perhaps guiding or protecting them in ways not seen in the original story.
Obviously, Bella is one of the main characters as she is in the role of the Volturi's mother. And the members of the Volturi like Aro, Caius, and Marcus are also likely to be main characters as they are the ones Bella has a relationship with in this new scenario.
In the Twilight universe where this fanfiction is based, the Volturi kings are Aro, Caius, and Marcus. They are the leaders of the Volturi, an ancient and powerful coven of vampires.
In some fanfictions, Bella Swan can be depicted as the Volturi's princess. Fanfiction allows for a lot of creative liberties, so authors can come up with all sorts of alternate storylines. It's not part of the original 'Twilight' canon, but it makes for an interesting concept in the world of fan - created stories.
There is also a possibility that a lone vampire, who has a sense of justice or who has been secretly observing Bella and has grown fond of her, decides to take on the Volturi and rescue her. This vampire could have some special abilities or knowledge that gives them an edge against the powerful Volturi.
It depends on different fanfiction works. Some may write it very well, creating exciting storylines around Bella in this role. They might explore her leadership, her relationships within the Volturi, and how she adapts to the new position. However, others may not do as good a job, perhaps lacking in character development or creating unconvincing scenarios.
There could be other vampires that Bella meets during her time as a vampire before the Volturi. For example, some lone vampires who are also trying to stay out of Volturi's radar. They could become her allies or foes depending on their motives.
One idea could be that Bella Swan's cousin, who is unaware of the vampire world at first, travels to Italy for some reason. There, by chance, they meet a Volturi member. The Volturi member is initially intrigued by the cousin's unique scent or personality. As the story progresses, they start to develop a bond that defies the Volturi's strict rules about relationships with humans. This could lead to a lot of internal conflict within the Volturi and also put the cousin in danger from other vampires who don't approve of this relationship.
Power is a common theme. The Volturi are a very powerful coven, and Bella's relationship with them often involves her dealing with their power. Another theme is loyalty. Bella has to decide where her loyalties lie - with the Cullens or with the Volturi. And of course, love. Whether it's her love for Edward or some new relationships she forms within the Volturi world.
Well, it depends on the specific fanfiction. There are countless fanfictions out there, and while the idea of Bella Swan being a Volturi member is not part of the original Twilight canon, some authors like to take creative liberties. In some cases, she might be a reluctant Volturi member, forced into their ranks for some reason. In others, she could be a willing participant, drawn by their power and mystery.