One common trope is the vampire's alluring and seductive nature. Their charm often draws the human characters in. Another is the idea of the vampire's immortality adding an element of mystery and a different perspective on time and relationships. Also, the concept of blood - drinking being an erotic act in itself, with the sharing of blood symbolizing a deep connection between the vampire and their lover.
Well, a popular trope is the forbidden love aspect. Since vampires are often seen as dangerous and different from humans in these stories, a relationship between a human and a vampire is considered taboo. And then there's the power dynamic. Vampires usually have more power, physically and sometimes supernaturally, which can create an interesting dynamic in romantic or sexual relationships within the fanfiction. There's also the transformation trope, where a human might be turned into a vampire, and that process can be intertwined with erotic elements.
A popular trope is the vampire with a heart of gold. Despite being a creature of the night, they have a soft side, especially when it comes to a particular human. It's a way to add depth to the otherwise menacing vampire character.
One popular trope is the 'enemies to lovers' scenario. In both Charmed and Vampire Diaries, there are characters with opposing views or allegiances that fans like to pair up romantically. For example, in Vampire Diaries, a fanfiction might explore the relationship between a vampire and a vampire hunter who start off hating each other but gradually fall in love. Another trope is the 'alternate universe' where the story takes place in a completely different world from the original shows, like a world where the witches in Charmed have different powers or the vampires in Vampire Diaries don't have to feed on blood. And the 'time - travel' trope is also common, where characters go back in time to change events in the shows' histories.
One popular trope is the 'powerful - being - in - a - human - world' trope. Since both Rosario Vampire and Witchblade involve supernatural elements, fanfiction often plays with the idea of these powerful characters (vampires, witches, etc.) trying to fit into or interact with the normal human world. Another is the 'forbidden love' trope, as Rosario Vampire has a lot of complex relationships that can be explored further in fanfiction.
In Kara and Lena vampire fanfiction, a common trope is the power struggle. Vampires usually have superhuman powers. So, if Kara is a vampire, she might struggle with controlling her new powers, and Lena could be the one to help her. Another trope is the immortality factor. If Lena is a human in the story, the idea of Kara's immortality creates a sense of longing and melancholy. And of course, the 'blood bond' trope where the sharing of blood between them has a special significance.
One popular trope is the crossover aspect itself. Writers often like to bring the characters from Spider Man and Vampire Diaries together in unexpected ways. For example, having Spider Man face off against the vampires in Mystic Falls. Another is the 'fish out of water' trope, like if Peter Parker somehow ended up in the Vampire Diaries' universe and had to adapt to its rules.
One common trope is the 'forbidden love' aspect. A vampire might fall in love with a human, and their need to drink blood creates a lot of tension in the relationship. Another is the 'vampire society' trope, where the story delves into the politics and hierarchies among vampires. Also, the 'vampire hunter' trope is popular, adding an element of danger and conflict as the hunter tries to stop the vampire from drinking blood.
One popular trope is the 'fish out of water' aspect as Tsukune, a human, is in a school full of monsters. Another is the development of his relationships, like his romantic relationship with Moka. There's also the trope of him having to prove himself in a world where he's initially seen as weak.
One popular trope could be the 'outsider' trope. Pearl and Jonathan might be seen as outsiders in the vampire community, and the fanfiction could revolve around them trying to find their place. Another is the 'redemption' trope, where they might have done something wrong in the past and are now seeking redemption.
The 'time - travel' trope can be seen in some fanfictions. A character from 'Vampire Diaries' might travel back in time to the era of 'Merlin' and change the course of events. Or vice versa. The 'hidden identity' trope is also popular. A character might be hiding their true identity as a wizard from 'Merlin' in the 'Vampire Diaries' world. And the 'battle of powers' trope, where characters from both series test their powers against each other to see who is stronger.
One popular trope is the 'enemies to lovers' scenario. For example, a vampire and a hunter might start off hating each other but gradually fall in love. Another common one is the 'soulmate' trope, where two characters are fated to be together. And of course, there's the 'redemption' trope, where a character who has done bad things tries to make up for it.