They're popular because they offer a fresh take on the well - known Harry Potter story. By changing his family situation through adoption, it can completely shift the dynamics of the story.
One common theme is identity. Since Harry is adopted, he may struggle with who he really is in relation to his new family and his wizarding heritage. Another theme could be family dynamics, as he has to adapt to a new family structure. And there's often the theme of secrecy, as his adoption might be something that needs to be hidden for some reason in the wizarding world.
In this kind of fanfiction, Harry often becomes more proficient in potions and other areas that Snape is good at. His relationship with Snape also makes him more empathetic towards Snape's past and the Slytherin house in general. He may not be as quick to judge people based on their house. Also, he might develop a more complex view of the wizarding world's politics, as Snape is deeply involved in some of the darker aspects of it.
His character would likely become more edgy and darker. Growing up with demons, he'd be exposed to a lot of negative and cruel things, which would change his view of the world.
Harry would develop a more diverse set of values. Ahsoka comes from a different cultural and moral background in the Star Wars universe. So, he might start to see magic and power in a different light. He could become more in tune with nature and the Force, which would add new layers to his character. Also, his sense of loyalty would expand beyond his friends at Hogwarts to include those he meets in the Star Wars universe through Ahsoka.
Often, Harry's development is more complex. He has to deal with two different worlds, the muggle world where he was raised and the wizarding world he belongs to. This dual - world experience can make him more adaptable but also more conflicted. For example, he may love his muggle family in some ways but also feel a sense of betrayal when he realizes they've been trying to keep him from his true nature. His relationships with other characters, like Hermione and Ron, may also be different as he has this unique background.
Harry's character would likely become more independent and self - reliant. Alduin may not coddle Harry like some of his Hogwarts mentors did. He'd have to learn to fend for himself in a strange new world. His sense of adventure would be heightened as he explores Alduin's domain. Also, his view of magic would expand greatly, which could make him more confident in his abilities.
The fanfiction 'Harry Potter adopted by vampires' could be really interesting. Harry would be exposed to a very different culture. Vampires are often depicted as nocturnal, so Harry might have to adjust his sleep schedule. His magical abilities could interact in unexpected ways with vampire characteristics. He might also face discrimination or fear from both the wizarding world (who may not trust vampires) and the vampire world (who may not trust a wizard). It could be a story full of conflict, self - discovery, and new friendships as he tries to find his place in this strange new world.
One possibility is that Harry Potter, in this fanfiction, might be exposed to a whole new set of dark magic and powers that demons possess. The demons could see his potential and decide to raise him in a way that is completely different from the wizarding world he knew. Maybe they would teach him to use his magic more aggressively or in ways that are considered unethical in the normal wizarding community.