Obviously, Harry Potter himself would be the central character as he is the one undergoing the transformation into a born vampire. His friends like Hermione and Ron would also be important characters. They would likely play a role in either helping Harry adjust or being conflicted about his new state.
One possible plotline could be Harry struggling to control his new vampire instincts while still trying to protect his friends at Hogwarts. He might have to deal with the thirst for blood while attending classes and facing off against the Dark Arts. Another could be that he discovers a whole new vampire community within the wizarding world that has its own rules and power structures.
In a 'Harry turns into a vampire' fanfiction, the story could start with Harry being cursed by a powerful and ancient spell that turns him into a vampire. His friends at Hogwarts are initially scared and unsure how to deal with him. However, Harry is determined to find a way to reverse the transformation. Along the way, he discovers that there are some positive aspects to being a vampire, such as heightened senses that help him in his detective - like investigations into the origin of the curse.
It could be a powerful vampire clan that doesn't want Harry, a new vampire, to disrupt their ways. They might try to either kill him or force him to join their ranks against his will. They could see him as an outsider who doesn't belong in the vampire world and a potential danger to their secrecy.
Maybe Draco is jealous of Harry's popularity and power. Turning him into a vampire could be a way to strip him of his status among the wizarding community. Vampires are often feared and shunned, so Draco might think this would be a good way to get back at Harry.
One possible plot could be that Harry, as a vampire, has to hide his true nature at Hogwarts. He might struggle with the urge to drink blood while being surrounded by his wizard friends. For example, during potions class, the smell of certain ingredients could trigger his vampire instincts, making it difficult for him to focus. And he may have to find a way to obtain blood without raising suspicion, perhaps by befriending some magical creatures that can provide a substitute or by secretly using his vampire powers to hunt small, non - magical animals in the Forbidden Forest.
In such a fanfiction scenario, Harry might have enhanced physical abilities like super strength and speed from the start. He could also have a natural allure, which might make his relationships with others more complex. His magical abilities might be influenced too, perhaps having a different connection to certain spells related to darkness or life-force.
Well, if Snape turns Harry into a vampire in fanfiction, it would completely change the dynamic. Harry would have to deal with new instincts like the thirst for blood. His relationships would be strained as his friends might be scared of him. Also, his role as the 'Chosen One' would be redefined as he's now a different kind of being with different needs and abilities. He might have to struggle between his human side and his new vampire nature.
Well, it could be really interesting. He might have different powers compared to his wizard self. For example, he could have enhanced strength and speed. Also, his relationship with other characters would change. Instead of using a wand for magic, he might have some vampire - related magic. And his appearance would be different too, with pale skin and fangs.
Hermione would probably be both curious and a bit cautious at first. She'd immediately start researching about vampire - wizard hybrids in the library. Ron, on the other hand, might be more freaked out. He's used to the normal wizarding world, and a vampire Harry would be a big shock. Dumbledore, being the wise and accepting figure, would likely see Harry's vampire nature as an opportunity for him to learn more about different magical beings and help bridge the gap between vampires and wizards. He'd offer his guidance and protection.