The relationship in fanfiction can be very diverse. Some fanfictions portray it as a slow - burn romance. Marcus, being an ancient vampire, has a lot of past baggage, and Bella has her own issues with the vampire world. They start by having simple conversations, gradually getting to know each other better. In other stories, it's more of a friendship - based relationship. They might start to protect each other from the threats within the Volturi or from other vampires. And in some more creative fanfictions, their relationship is based on a shared spiritual or magical connection that is unique to them and helps them grow both as individuals and as a pair.
In some fanfiction, their relationship develops quickly. They might share a moment of intense eye contact and instantly feel a deep connection. From there, they start spending all their time together, getting to know each other's likes and dislikes.
One great 'bella swan and marcus volturi fanfiction' is 'The Unlikely Bond'. In this story, Bella discovers a different side of Marcus that she never expected. Another one could be 'Marcus' Redemption'. It shows how Marcus tries to break free from the Volturi's dark ways because of Bella's influence. And 'A New Alliance' is also interesting, where Bella and Marcus form an unexpected alliance to face common threats in the vampire world.
One popular Marcus Volturi and Bella Swan fanfiction might be those where Marcus sees Bella's unique allure beyond the normal vampire - human dynamic. For example, in some stories, Marcus becomes her protector in the Volturi world, guiding her through the complex politics of the vampire clans.
Fans might be drawn to it because Marcus represents a different aspect of the vampire world. He has a certain mystery and age - old wisdom. When paired with Bella, it creates a contrast. Bella is young and new to the vampire world, and Marcus can introduce her to the deeper, more complex parts of it. Also, it can provide a chance to explore what would happen if the Volturi had a more personal connection to Bella rather than just seeing her as a potential threat or an oddity.
In some fanfictions, their relationship starts with an instant attraction. Maybe it's a look across the room at a vampire gathering that sets things off. From there, they start to spend time together, getting to know each other better.
In many fanfictions, Bella starts to understand the complex world of the Volturi better. She learns about their laws, politics, and hierarchies. Caius, in turn, begins to see Bella not just as a mate but as an equal. He might start to value her opinions more and include her in Volturi affairs. For instance, Bella could use her knowledge of the human world to help Caius make decisions regarding vampire - human relations.
In some fanfictions, Bella's character might become more confident. As an immortal, she no longer has the same fears of mortality. For example, she could be more fearless in facing dangerous situations.
They could start off with a bit of friction as they are likely to have different personalities. But over time, they would grow closer. Maybe through shared experiences like going to school together or dealing with family problems.
It could start with animosity. Caius might see Bella's cousin as a potential threat or just an annoyance at first. But then, as he gets to know her better, he realizes she has a kind heart. He starts to protect her from other vampires or dangers in Forks, and slowly, feelings of love or at least deep affection develop.
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.