Perhaps he's adopted by a family of house - elves. They teach him their unique brand of magic that is more about domestic and hidden spells. Harry would then have a different perspective on the wizarding world, seeing it from the eyes of those who serve. He could also use this knowledge to help other house - elves gain more rights later on.
The plot could involve Harry Potter having a special connection with magical creatures that no one else has. He might discover a new type of magical creature and learn its secrets, which could help him in his fight against the dark forces.
Thestrals could also be the ones to adopt Harry. Since they are associated with death and are only visible to those who have witnessed it, Harry's connection to death (losing his parents) could make a bond with them. They could teach him how to move unseen and sense things that others can't, which would be a great advantage in the wizarding world.
They could encounter a Hippogriff. These magnificent creatures are both proud and dangerous. The twins might have to learn how to approach it correctly, like Harry did with Buckbeak. Another possibility is a Niffler. Given their love for shiny things, it could create some interesting situations if the twins are around one. Maybe they're trying to retrieve something a Niffler has stolen. Thestrals are also an option. Since they can only be seen by those who have witnessed death, if the twins have had such an experience, seeing a Thestral could be a very poignant moment in the fanfic.
In some Harry Potter fanfics, you might find unique magical creatures like the Shrieking Shackle. It's a small, furry creature that can emit a high - pitched shriek to stun predators. Another could be the Glimmerwing, a butterfly - like creature with the ability to turn invisible when it senses danger. These add new and exciting elements to the magical world already established in the original series.
One possible plot could be that Marge, despite her initial rough exterior, discovers a soft spot for Harry. She might start to teach him some of her own values, which could be a mix of traditional and rather strict ones. Harry would have to adjust to living in a new environment with Marge's dogs and her no - nonsense attitude.
It could be that the wolves are actually magical wolves with special powers. They sense Harry's unique magic and choose to protect him from the threats he faces in the wizarding world. Harry, while being adopted by them, might discover new forms of magic that are related to nature and the wild, which are different from what he learns at Hogwarts.
One possibility is that Umbridge, despite her cruel nature, sees some potential in Harry for her own gain. Maybe she tries to mold him into a perfect little wizard according to her strict and often wrong ideas. She could isolate Harry from his friends and force him to follow her rules blindly, which would create a lot of internal conflict for Harry as he tries to resist her brainwashing while living under her roof.
In a 'Harry Potter adopted by Newt' fanfic, perhaps Newt gets a mysterious message about a powerful but troubled young wizard. When he finds Harry, he realizes that the boy has a connection to the magical creatures world that he doesn't yet understand. Newt takes Harry under his wing. Harry gets to live in Newt's home, which is filled with all sorts of amazing and dangerous creatures. He learns about their habitats, behaviors, and how to communicate with some of them. This knowledge and his bond with Newt could change the way he approaches challenges at Hogwarts and in the wizarding world as a whole.
Well, the basilisk is a very prominent magical creature in Harry Potter fanfic. It's a giant serpent that can kill with a single glance. Fanfic writers often explore its origin and the mystery surrounding it. Also, the centaurs are quite interesting. They are half - human and half - horse, and in fanfics, they can offer unique perspectives on magic and the wizarding world.
In Harry Potter fanfic, one interesting magical creature is the Occamy. It's a serpentine - like creature with wings and can grow or shrink to fit available space. Another is the Nundu. It's a large and dangerous beast, said to have a breath so poisonous it can wipe out entire villages. And the Thestral, which is often explored in fanfic in more detail, as it's only visible to those who have witnessed death.