A third idea is that the OC is a vampire from a different coven that has a long - standing feud with the Volturi. However, she is captured by them. Instead of killing her, the Volturi Kings are drawn to her beauty and strength. As she stays with them, she begins to see a different side of the Volturi, and a love story unfolds despite the initial enmity between their groups.
One idea could be Bella having to prove her loyalty to the Volturi kings in a series of dangerous trials. Another could be a love triangle between Bella and two of the Volturi kings. Maybe she discovers a hidden power within herself that the Volturi are interested in.
To create a strong OC, consider giving her unique abilities. It could be something like telepathy but with a twist, like she can only read the minds of vampires when they are in a certain emotional state. In terms of appearance, make her stand out. Maybe she has a very rare hair color or eye color that is not common among vampires. And her values should be clear, like she values loyalty above all else, which would play into her relationships with the Volturi Kings.
A theme of mystery also prevails. The Volturi world is full of secrets, and the OC often finds themselves uncovering these secrets. For example, in some fanfictions, the OC discovers hidden agendas within the Volturi hierarchy. And there's also the theme of identity. The OC has to figure out their place in the Volturi - dominated world, which can be a journey of self - discovery.
A common theme is power. The Volturi kings are powerful, and when an OC is introduced, it often involves power struggles or sharing of power. Another theme is love and attraction. Since the Volturi kings are alluring, there are many stories about the OC falling in love with them or vice versa. Also, the theme of loyalty often comes up. The OC has to decide whether to be loyal to the Volturi or their own beliefs.
One idea could be that the OC is a healer who stumbles upon Frankenstein's monster in the woods. The OC decides to help the monster, despite the danger, and they form an unlikely bond. This could lead to a story of redemption for the monster and a journey of self - discovery for the OC.
Maybe the OC is a scientist who has developed a device that can temporarily steal The Flash's speed. At first, the OC uses it for personal gain, but then realizes the chaos it's causing in the city. They then team up with The Flash to take down other villains who are after the device. Or, the OC could be a meta - human with the ability to see the future in flashes. The Flash initially doesn't trust the OC, but as they start to have the same visions, they have to work together to prevent a major disaster from happening.
The OC could be a psychic who is unknowingly drawn to Derry because of Pennywise's presence. Their psychic powers allow them to sense Pennywise's energy but not fully understand what it is at first. As Pennywise tries to manipulate the OC, the OC starts to fight back using their psychic abilities, creating a battle of wills and powers that could span across different dimensions within Derry, from the sewers to the abandoned houses and the mindscapes of both characters.
The OC could be a researcher studying digimon behavior. Renamon becomes the subject of the study. At first, Renamon is very guarded around the OC. However, as the OC shows genuine respect for Renamon and her kind, Renamon begins to open up. They then embark on a journey to discover more about the history of digimon, with their relationship growing stronger along the way.
Well, an interesting plot could involve an OC that is a transfer student, just like the protagonist. But this OC has a hidden past related to the Metaverse. Maybe they were experimented on by a shadowy organization in their home country, and this gives them a different perspective on the Metaverse compared to the Phantom Thieves. Their goal could be to find out who was behind those experiments and get revenge. Along the way, they form a bond with the group and learn new ways of using their powers.
One idea could be that the OC is a new Keyblade wielder who meets Ventus during his training. They start as rivals, constantly competing in battles and challenges. But as they face a powerful enemy together, they realize their combined strength and start to develop feelings for each other.