One possible plot twist could be that Sirius Black, being a wanted man, has to constantly move with Harry to avoid capture. This would make Harry's childhood very different from the one at the Dursleys. He'd grow up learning about the wizarding world on the run, perhaps meeting some unique characters in hiding places.
Maybe Sirius decides to train Harry in advanced magic much earlier than in the original story. Since Sirius was a skilled wizard, he could teach Harry some dark - arts - defense spells that are not usually taught in Hogwarts at a young age. This could make Harry a more formidable wizard when he finally enters Hogwarts.
A major plot twist could be that Sirius manages to clear his name much sooner. With Harry by his side, they could expose the real traitor in the Order of the Phoenix together. This would change the whole dynamic of the wizarding world's view towards Sirius and Harry, and they might be able to live a more stable life in the wizarding community.
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.
Well, perhaps the Black family's dark magic artifacts play a huge role. Harry could be exposed to them at a young age. He might start to show an aptitude for certain types of dark magic not seen in the regular series. But then he has to struggle with whether to embrace this power or reject it, knowing it goes against what Dumbledore and others would expect.
One possible main plot twist could be that Sirius manages to completely hide Harry from the wizarding world's prying eyes until he comes of age. This would mean Harry grows up without the constant threat of Voldemort's followers finding him. Another twist could be that Sirius discovers some long - hidden magic within Harry that was dormant because of his upbringing with the Dursleys, but flourishes under Sirius's care.
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.
A really interesting plot twist could be that the phoenix, being a symbol of rebirth, has the ability to make Harry remember his past lives. This would give him an edge as he could draw on the knowledge and skills from his previous existences. He might remember spells and strategies that were long forgotten, which would completely change the course of his fight against the dark forces.
Well, a really interesting plot twist could be his relationship with the other Hogwarts houses. He might not have the same automatic connection with Gryffindor. Instead, he could be more inclined towards Slytherin values, which would completely change his dynamic with Ron and Hermione. Maybe he would form closer friendships with Slytherin students right from the start. Also, his views on pure - blood supremacy could be more complex as he is raised in a family that might have some traditional views on blood purity.
Well, perhaps the nuns are in cahoots with some magical creatures. They could be working with a group of centaurs who have prophesied that Harry must be raised in seclusion among the nuns to gain a certain kind of purity of spirit. Then, when Harry finally enters the wizarding world, he has an aura about him that both attracts and confounds the dark forces. He might also have a special connection to the magical animals due to his time with the nuns, like being able to communicate with them on a deeper level, which would be really useful in his battles against the dark side.
One possible plot twist could be that Kenpachi's rough and battle - hungry nature makes Harry a much more aggressive wizard. Instead of waiting for Voldemort to come to him, Harry might actively seek out dark wizards to fight. Another twist could be in the way magic is taught. Kenpachi, not being from the wizarding world, might introduce Harry to a more physical and unorthodox way of using magic, like using brute force in spellcasting rather than the traditional finesse. Maybe Harry would also develop a more carefree attitude towards the rules of the wizarding world, much like Kenpachi does with the Soul Society's rules.
A plot twist could be that Madame Maxime, being half - giant, imparts some of her physical and mental toughness on Harry. This makes him a more formidable opponent in duels and other challenges. In the story, this might lead to him being targeted earlier by Voldemort's forces because they see him as a greater threat. Also, the Beauxbatons Academy environment, which he would be more familiar with due to being raised by Madame Maxime, could have different magical traditions. These traditions could either help or hinder Harry when it comes to facing the Dark Lord. For instance, they might have different ways of casting defensive spells that Harry has to adapt to the British magical world.
The plot could take a really interesting turn when it comes to Voldemort. Since Snape is raising Harry, he might train Harry in a way that Voldemort doesn't expect. Maybe Harry would be more of a spy in the dark side's camp. Snape could also use his position to mislead Voldemort about Harry's true abilities and intentions. This would create a whole new set of challenges and power dynamics in the fight against the Dark Lord. Harry's loyalties would be constantly tested, and his relationship with Snape would be even more crucial to the story.