One plot idea could be that Harry is raised by Dementors. He might grow up with a very different view on life and magic. Since Dementors feed on positive emotions, he could struggle to understand concepts like love and friendship in the same way as in the original story. Another could be if he was raised by a group of Acromantulas. He'd likely be more in tune with the Forbidden Forest and its secrets, and might have a natural ability to communicate with spiders, which would be a very strange and unique power compared to his normal Gryffindor traits.
Perhaps if Harry was raised by a Basilisk. He would have to learn to coexist with such a dangerous creature from a young age. He could develop some immunity to its deadly stare over time. This would make his time at Hogwarts extremely interesting as he would have this connection to a dark and feared creature that most others would be terrified of. Also, it could lead to a very different dynamic with the other students and teachers, as they would be both curious and cautious about his upbringing.
If Harry was raised by Inferi, it would be a very dark take. He might not have a full understanding of his own humanity. He could have an eerie presence and strange powers related to the dark magic that animates Inferi. His relationships at Hogwarts would be very strained as people would be rightfully afraid of him. His journey would be about trying to break free from the influence of the Inferi and discover his true self as a wizard with a capacity for good, which would be a very different kind of hero's journey compared to the original Harry Potter story.
One idea could be Harry being raised by the Weasleys from a very young age. He'd grow up with their large family dynamic, learning magic in a more chaotic but loving environment. It might change his personality a bit, making him more outgoing and confident earlier. Another plot could be him being raised by Remus Lupin. Lupin would instill in him a deep understanding of the dark arts in a more academic way, and also teach him about acceptance of his own lycanthropy - like condition if he were to inherit it. And a third idea is Harry being raised by the centaurs in the Forbidden Forest. He'd learn their unique brand of magic, which is more in tune with nature, and have a different perspective on the wizarding world and its relationship with the natural world.
Well, he could be raised in a small, idyllic French village full of magic. The local wizards there might be more in tune with nature magic. So, Harry grows up learning how to communicate with magical creatures in the French forests in a way that's different from what he'd learn in Britain. Maybe there's a mystery about his parents in the French wizarding world too. Like, they were involved in some secret mission in France before they died, and as he grows up, he starts to uncover clues about it.
One idea could be that they grow up learning magic together in a unique way. Maybe they discover a new spell or form of magic that no one else has. Another plot could involve them facing a common enemy from a young age and having to rely on each other's unique skills. For example, Fleur's Veela charm and Harry's Gryffindor courage could combine to defeat the foe.
One idea could be that Harry is raised by a group of centaurs. They teach him their wisdom about the stars and nature. He grows up with a deep understanding of the forest and its magic, and when he goes to Hogwarts, he has a different perspective on magic compared to the other students. For example, he might be more in tune with natural magic and have an easier time in Herbology and Care of Magical Creatures classes.
One idea could be a story about a young wizard who discovers a new, rare magical creature in the Forbidden Forest and tries to protect it from dark wizards who want to use its powers for evil. Another could be a fanfic where a group of Hogwarts students form a club dedicated to studying and caring for magical creatures, and they encounter various challenges and adventures along the way. A third idea is a story that focuses on the relationship between a magical creature and a character who has the ability to communicate with it telepathically, and how they work together to solve a mystery at Hogwarts.
One plot idea could be that Harry discovers unique magical creatures that exist only in space. For example, there could be a species of floating, star - like creatures that can communicate through light pulses. Another idea is that he has to learn to control his magic in zero - gravity, which presents a whole new set of challenges compared to on Earth. Maybe he also forms an alliance with alien races who are also magically inclined and together they fight against a common dark force that threatens both the wizarding world and the galaxies.
Perhaps the monster has a vendetta against certain wizarding families, and as Harry grows up under its care, he is caught in the middle of this conflict. He has to decide whether to side with the monster or try to find a way to reconcile the differences. This could lead to a whole new set of adventures and challenges for Harry.
Perhaps they are raised by a powerful and kind wizard who instills in them values of love and friendship. This causes Tom to view magic in a different light. They might go on adventures together in Hogwarts, exploring the secrets of the castle. Harry could be the one to show Tom the importance of loyalty, and in turn, Tom could share his advanced knowledge of magic with Harry.
One interesting plot idea could be that Snape raises Harry with a strict but fair hand. He teaches Harry about the Dark Arts not to encourage him to use them, but to make him fully aware of the dangers. Harry might grow up with a more nuanced view of Snape from the start, and their relationship could be a mix of father - son dynamic and teacher - student. For example, Snape could train Harry in potions from a very young age, leading Harry to become a master of potions himself much earlier than in the original story.
One interesting plot idea could be that Snape, in raising Harry, teaches him advanced potions from a very young age. Harry becomes a prodigy in potions, much to the surprise of the other Hogwarts students. Another idea is that Snape's strict but fair upbringing makes Harry more reserved and less impulsive, which changes the way he interacts with his friends. He might be more cautious and calculating in his actions, especially when dealing with enemies like Voldemort.