To develop Demetri further, you could explore his past. Maybe he had a human life before being turned that he barely remembers, but certain events in the fanfiction could trigger those memories, adding depth to his character. For Heidi, you could show more of her vulnerability. She's often seen as this seductive figure, but what if she has insecurities about her role in the Volturi?
One idea could be a story where Demetri and Heidi are sent on a secret mission by the Volturi. They have to infiltrate a group of rogue vampires who are causing chaos in a small town. Along the way, they start to question their loyalty to the Volturi as they see the good in the town's people.
One common theme is love. Often, the OC falls in love with Demetri or vice versa, and the story revolves around their relationship. Another theme is power. Since Demetri is a vampire with certain powers, the OC might have powers too, and their powers interact. Also, there's the theme of belonging. The OC usually has to find their place in the Twilight world.
The characters themselves are very interesting. Demetri with his tracking abilities and Jane with her unique power of causing pain through illusion. Fanfiction allows writers to explore their backstories and relationships in more depth than the original books or movies. For example, a fanfic might delve into Demetri's life before he became a vampire.
Well, there are also some dedicated Twilight fanfiction forums out there. These forums often have sections specifically for fanfictions about different characters. You might have to register on some of them, but it's worth it. Once you're in, look for threads related to Demetri and Jane. Members often discuss and share their favorite fanfictions in these threads, which can lead you to some great reads that you might not find on the more mainstream platforms.
Maybe in a fanfiction, Demetri discovers that Bella has a hidden power that not even the Cullens are aware of. He then has to decide whether to report it to the Volturi or keep it a secret and help her develop this power. This could create a complex relationship between them, full of trust issues and moral dilemmas.
Well, there's 'Demetri and the Mysterious OC'. In this fanfiction, the OC has a special power that draws Demetri in, and it creates a really interesting dynamic. It delves deep into the Twilight universe and how an OC can fit into it. Also, 'A Twilight Encounter' is quite good. The author does a great job of building a connection between Demetri and the OC through a series of exciting events.
At first, their relationship might be full of tension. Demetri is a vampire and Leah is a werewolf. But as they interact more, they could find common ground in their loyalty to their respective groups. They might start to communicate secretly to avoid causing chaos between vampires and werewolves.
One idea could be Demetri and Leah teaming up to protect the Forks area from a new threat that neither the vampires nor the werewolves have faced before. They might start off as reluctant allies but gradually develop respect for each other.
Another way is to put them in situations that challenge their loyalty to the Volturi. In the Twilight world, the Volturi are very powerful and feared. But if Jane and Demetri are faced with a situation where they have to choose between doing what the Volturi want and what they believe is right, it would show different aspects of their characters. They could also interact more with other characters outside of the Volturi, which would force them to adapt and grow.