You can start by giving him a unique backstory. Maybe he grew up in a wizarding family with a dark secret that he's trying to uncover. This would give him a sense of purpose.
Give him some distinct personality traits. For instance, he could be extremely curious but also a bit of a loner. This would make his interactions with other characters more interesting. He might be the type to explore the Forbidden Forest alone just to satisfy his curiosity. And when he does interact with others, his loner nature could lead to some awkward but also endearing moments. He could also have a strong moral compass that sometimes conflicts with the rules of Hogwarts, making for some great internal and external conflicts in the story.
Think about his skills and abilities. Maybe he has an uncanny ability to communicate with magical creatures that most others don't. This could lead to him befriending a dangerous creature that the other students are afraid of. His skills could also put him in the spotlight, either for good or bad. If he uses his skills to help solve a problem at Hogwarts, he could become a hero. But if he uses them in a way that goes against the school's wishes, he could be in trouble. All of these aspects would help develop the character of Corvinus in your Harry Potter fanfiction.
In the fanfiction, Corvinus could be a transfer student from a different magical school that has a very different approach to magic. His arrival at Hogwarts could introduce new types of magic and magical creatures that the Hogwarts students have never seen before. He could also have a different set of values and beliefs about magic, which could cause some clashes and also some interesting exchanges of ideas among the students.
Harry would likely develop a very different personality. He may be more solemn and less prone to the typical teenage angst that the original Harry had. Since he is raised by Death, he might be more in tune with the darker aspects of life and magic from a young age.
In this fanfiction, Harry's development could be centered around his understanding of family. Growing up with a scorpion, he has a very different concept of what a family is. This could lead to him having a complex relationship with the Weasleys or other surrogate families in the wizarding world. He might be hesitant to accept their love and care at first, but gradually come to realize the value of a real family. Also, his magical development could be more instinctive, like how a scorpion reacts instinctively to threats, Harry might use magic in a more impulsive yet effective way when in danger.
Harry's character would undergo a significant transformation. The Cullens' values of self - sacrifice and protecting the family would influence him. He'd likely become more empathetic towards non - human beings. His magic might be used in more creative ways to adapt to the Cullens' lifestyle. For instance, he could use magic to make their home more vampire - friendly. His confidence would grow as he learns from the Cullens' strong family bond.
He would likely be more confident. Growing up with gods would give him a sense of self - assurance that he lacks in the original story. He might be less hesitant in using his powers.
His character would be more assertive. He'd be used to taking action quickly due to his Warrior upbringing. He might be less hesitant in difficult situations compared to the original Harry.
His character would be more stable. Without the Dursleys' abuse, he would be less angry and more trusting.
Harry's character would likely become more hardened. In Mandalore, he'd face different challenges than in the wizarding world. He'd have to be more physically tough, which would make him more confident in his own abilities. His sense of justice would also expand as he learns about the Mandalorian code. He might become more of a lone wolf, relying on his own skills rather than always having his friends by his side as he did in Hogwarts.
In this kind of fanfiction, Harry would develop a very different set of values. Growing up with pirates, he'd value things like loot, loyalty among the crew, and freedom of the seas. His sense of justice might be more like a pirate's idea of justice - rough and ready. He'd be bolder in his actions and less likely to wait for permission or guidance. For instance, if he saw something wrong at Hogwarts, he'd take matters into his own hands immediately rather than go through proper channels. He'd also have a more salty language perhaps, and his interactions with other students would be interesting as he tries to fit in while still holding onto his pirate - raised ways.
He develops a more rebellious streak. In the original, Harry was quite respectful of authority in the wizarding world. But being raised by bikers, he might question rules more often. For example, he might not be as quick to follow Hogwarts' strict regulations.