One possible plot twist could be that Harry, under Bellatrix's influence, becomes a much darker and more ruthless wizard. Bellatrix might train him in the Dark Arts, and he could end up being a sort of anti - hero. He might have a completely different view of the wizarding world and be at odds with his former friends from Hogwarts.
Harry could become more secretive and distrustful. Growing up with Bellatrix, who is part of the Death Eaters and has a lot of secrets, Harry would learn to keep things to himself. He may not trust others easily, even those who seem friendly, as he has been brought up in an environment full of lies and hidden agendas.
Harry might be more secretive. He'd have to hide any doubts or conflicting feelings he has about the dark path he's being led down. Bellatrix would not tolerate any signs of weakness or deviation from her plans. So, he'd become very good at hiding his true self, which would make his personality complex and full of contradictions.
If Harry Potter was raised by Bellatrix, he would likely grow up in a very dark and twisted environment. Bellatrix is a Death Eater, so Harry would be exposed to the dark arts from a young age. His values and beliefs would be very different from the ones he has in the original story. He might not have the same sense of right and wrong, and could be more inclined towards the use of dark magic.
One possible storyline could be that Bellatrix, despite her dark past, has a change of heart due to some magical influence or a deep - seated love for the Potter family. Sirius, of course, would be a positive influence. They might raise Harry in a more unorthodox way, teaching him both light and dark magic in a balanced way so he can understand the full spectrum. This could lead to Harry being a more powerful and empathetic wizard, able to bridge the gap between different magical factions.
Another plot twist could be that Bellatrix realizes she has created a powerful adversary in Harry. As she raises him to be Lord Black, she instills in him a sense of power and ambition. But Harry uses that power not for the dark purposes she intended. Instead, he decides to reform the Black family traditions and bring a new era of inclusiveness to the wizarding world.
One possible plot could be Harry growing up believing he is on the right side by following Bellatrix and the Death Eaters. But then he discovers some secrets about his real parents and starts to question everything he's been taught. This leads to an internal struggle as he tries to decide whether to stay with Bellatrix or break away and find his true identity.
Harry would likely learn dark magic. Bellatrix is a master of the dark arts, so she would teach Harry curses and hexes that are not typically taught at Hogwarts. He might learn how to use the Cruciatus Curse effectively, for example.
Well, for one thing, his view of the wizarding world would be completely different. Growing up with Bellatrix, he'd probably be taught that pure - blood supremacy was the right way. His relationships would also be altered. He might not have the same friends like Ron and Hermione. Instead, he could be surrounded by Death Eaters or those with dark leanings. His magical skills might develop in a more aggressive and unethical direction as Bellatrix would encourage using magic for domination rather than for good.
If Harry was raised by Bellatrix, his character would likely be much darker. Bellatrix is a Death Eater, so Harry would be exposed to dark magic and Voldemort's ideology from a young age. He might be more ruthless and less empathetic compared to the Harry we know. For example, he might not value friendship as highly since Bellatrix doesn't really understand the concept of true friendship. Also, his view of the wizarding world would be skewed towards the pure - blood supremacist ideas that Bellatrix adheres to.