Another option is a powerful vampire coven leader who wants to use Jacob for his own purposes. When Jacob refuses, the coven leader turns against him and becomes the main source of conflict in the fanfiction.
One idea could be that Jacob struggles to adapt to his new vampire instincts while still holding onto his old wolf pack values. He might have a hard time controlling his thirst around his former friends.
One possible scenario could be that Finn, after being turned into a vampire, struggles with his new identity. He might have to deal with the urge to drink blood while still holding onto his old values. For example, he could try to find alternative ways to satisfy his thirst that don't involve harming humans, like drinking animal blood.
One idea could be that Stiles is turned into a vampire against his will. Maybe he's attacked one night while out investigating something supernatural. As a vampire, he has to struggle with his new urges, like the thirst for blood, while still trying to be the same person his friends know. He might start to see the world in a different light, both literally and metaphorically, as his vampire senses heighten.
One possible story could be that Mimiko is bitten by a mysterious vampire one night while walking alone. She then starts to experience strange cravings and enhanced senses. At first, she's terrified, but as time goes on, she begins to embrace her new vampiric nature.
In 'Jacob imprints on a vampire' fanfiction, a common theme is the idea of transformation. Not just in the sense of physical transformation like the werewolf or vampire forms, but also in terms of personal growth. Jacob may have to transform his views on vampires because of his imprint. Also, the theme of sacrifice can be present. He might have to sacrifice certain aspects of his werewolf life for the sake of his imprinted vampire. And there's often the theme of a new world order. Their relationship could potentially change the relationship between werewolves and vampires as a whole.
One possible scenario in this fanfiction could be that Finn's transformation into a vampire brings out a whole new side of his personality. He might struggle with his newfound thirst for blood while still trying to uphold his heroic values. Maybe he teams up with Marceline, who is already a vampire, and she teaches him how to control his urges.
Well, in the fanfiction, Finn could be part of a secret vampire society. He'd have to learn their rules and customs. There might be a hierarchy among the vampires, and Finn would have to find his place. Maybe he'd be a special kind of vampire with unique powers that the others envy or fear, which would create a whole lot of drama and intrigue within the vampire community.
Well, it could start with Ethan being in a small town where vampires secretly live. He unknowingly gets involved with them and is turned into a vampire. After becoming a vampire, he discovers new powers within himself. He could have the power of super speed and strength. However, he also has to face the challenges of hiding his new identity from his family and friends, and at the same time, he has to learn how to survive in the vampire world which is full of rivalries and power struggles.
If Percy becomes a vampire, his relationships would change drastically. His friends from Camp Half - Blood might be afraid of him or try to find a way to 'cure' him. His relationship with Annabeth would be put to the test. She might be determined to save him, but also conflicted because of what he has become. And Percy himself would have to deal with the fact that he now belongs to a different 'species' so to speak.