A well - crafted plot that combines the two different universes is key. It could involve how their different supernatural worlds interact, like the vampires in 'Twilight' and the demons in 'Shadowhunters'. Maybe a situation where they have to use their unique abilities to solve a problem that spans both worlds.
One popular Bella Swan and Simon Lewis fanfiction is 'Unexpected Alliances'. It explores a unique scenario where Bella and Simon team up against a common supernatural threat in a world that combines elements from their respective fictional universes. It has great character development and an engaging plot.
A major element is the relationship between Bella and Diablo. It could be a relationship of enmity, where Bella is trying to stop Diablo's evil plans. Or it could be a more complex relationship where they have to work together for some reason. Also, the use of Diablo's lore, like the different types of demons and magic, is key in these fanfictions.
The plot usually involves some sort of crossover event that brings them together. It could be a magical anomaly or a common enemy. And then, how they navigate this new situation together, with their different powers (if any are carried over from their respective universes) and personalities, forms the bulk of the story. There's also often a lot of exploration of the different vampire lore from both universes.
Character development is also crucial. Bella's vulnerability and strong will, and Thor's heroic and sometimes brash nature need to be well - portrayed. Writers often explore how they change as they interact with each other, for example, Thor learning about Bella's human emotions in more depth.
A plot could revolve around Simon being a long - lost relative of Bella's. He shows up in Forks and his presence disrupts Bella's relationship with Edward. Simon has his own secrets about the supernatural world which Bella gradually uncovers, and she has to decide between the two different worlds she's now a part of.
Simon's character can be developed by exploring his backstory. If he has a troubled past, it can be revealed gradually as he gets closer to Bella. Also, his relationship with Bella can make him more empathetic or more guarded depending on how their interactions play out. For example, if Bella is initially suspicious of him, he might become more defensive in his behavior.
One key element is often the exploration of a new relationship dynamic. Since they are not a canon pairing, it's interesting to see how they interact. Another element can be the alteration of the existing story's setting to fit their relationship.
One key element is the power dynamic. Since Bella is a slave, there's an unequal power relationship with the vampires. This often leads to conflict and tension. Another is the exploration of the vampire world. We get to see different vampire clans, their rules, and how they interact with Bella.
One key element is the clash of different universes. Bella Swan comes from the relatively normal (compared to the Suicide Squad's world) world of Twilight. So, when she's thrown into the Suicide Squad's world led by the Joker, there's a big contrast in values, powers, and the general way of life. Another element is the relationship between Bella and the Joker. It could be a relationship of enmity, where the Joker sees Bella as a new plaything or an ally in some strange plan he has. Or it could be a more complex relationship where Bella tries to understand the Joker's madness and maybe even reform him. Also, the action and adventure elements are important. The Suicide Squad is known for its dangerous missions, and Bella getting involved in those adds a lot of excitement to the fanfiction.
The dialogue in a Bella Swan original fanfiction matters a great deal. Make sure it sounds like her. For instance, her hesitant and often self - deprecating way of speaking. Another element is the pacing. Since Bella's story in the original had a certain rhythm, try to maintain a similar feel in the fanfiction, not making things too rushed or too slow.