One possible plot twist could be that the goblins have their own motives for raising Harry. Maybe they see him as a key to some hidden treasure or power. They could be training him in secret goblin magic that no human wizard knows about.
Well, one possibility could be that Harry grows up with a very different set of values. Goblins are known for their love of gold and their shrewdness in business. So Harry might be extremely good at handling finances and valuing things in terms of their worth. He could also have a more aggressive and territorial nature, like the goblins. For example, he might be very protective of his 'territory' at Hogwarts, which could be his dorm or the Gryffindor common room.
Perhaps a plot twist could be that the magical creatures interact with Harry differently. In the original, they had a certain way of relating to him, but in this fanfiction, being raised as a black wizard might make some creatures more or less friendly towards him. Some might see him as a symbol of change in the wizarding world and be more drawn to him, while others might be suspicious. Also, the way Harry approaches magic could be different. He might draw on cultural magic that is unique to his black heritage, which could give him an edge in certain situations or make him a target for those who fear change.
He might be more shrewd. Goblins are known for their business acumen and cunning. So, Harry could be more calculating in his decisions, not as impulsive as in the original story.
Maybe Harry would have a different view on the wizarding world. Growing up with the Delacours, he'd be exposed to a more international magical community from a young age. So, instead of being so focused on the British wizarding world's problems like Voldemort, he might be more interested in international magical relations and how to unite different magical cultures.
One interesting plot twist could be that Kami's magic is so different from the wizarding world's that Harry develops entirely new spells. For example, he might be able to use nature - based magic in ways wizards never thought of. Another could be that Kami's values of honor and purity influence Harry to take a different stance on the fight against Voldemort, perhaps trying to redeem him first. Also, the magical creatures in Kami's world could interact with the ones in Harry's world in unexpected ways, like a friendly competition between a hippogriff and a kirin.
Well, perhaps the story could involve Harry learning the goblin ways of magic and combat. He might grow up with a unique perspective on the wizarding world, seeing things from the goblins' point of view. Maybe he'd have a special bond with goblin characters and use their knowledge to outwit his enemies later in life.
Well, a really cool plot twist could be that the Malfoys, who are raising Harry, actually start to change because of him. They become less prejudiced against non - pure - blood wizards. And Harry, in turn, uses his influence within the Malfoy family to bring about positive change in the wizarding world. It would be a complete turnaround from the original relationship between Harry and the Malfoys in the original series.
In these fanfictions, a really cool plot twist could be that Moody, because of his experience with the dark arts, has knowledge of a secret power within Harry that even Voldemort doesn't know about. He nurtures this power in Harry, which makes Harry a completely different kind of threat to the dark forces. Maybe it's a power related to the ancient magic of the founders of Hogwarts that was passed down in a way no one expected.
One interesting plot twist could be that Remus, being a werewolf, has to constantly protect Harry from those who fear his lycanthropy. This could lead to them having to constantly move, creating a nomadic lifestyle for Harry. Another could be that Remus teaches Harry different magic that is more in line with his own values, which might put Harry at odds with the traditional Hogwarts curriculum.
One possible plot twist could be that Harry has unique magical abilities related to the ocean. For example, he might be able to communicate with sea creatures, which could help him in his adventures. Maybe he discovers a hidden underwater wizarding community that has been isolated from the rest of the wizarding world for centuries. Another twist could be that his enemies, like Voldemort, have a hard time reaching him in the ocean, but they find a way to use the ocean's power against him in some unexpected manner.