Most likely, Harry Potter, Hermione Granger, and Ron Weasley will still be the main characters. After all, they are the central figures in the original series. But there could also be new characters introduced who are either part of their wealthy new circle or those who are affected by their millionaire status.
It's almost certain that Harry, Hermione, and Ron will be the main characters. Harry might be the millionaire due to some inheritance or newfound magical discovery. Hermione, with her intelligence, could be managing their finances or coming up with brilliant ways to invest their money. Ron could be the one who has the most fun with the money, buying all sorts of cool magical gadgets. Additionally, characters like Dumbledore or Snape might still be part of the story in some way, maybe as mentors or those who observe the changes in the main characters due to their wealth.
Harry Potter would probably be one of the main characters. He's the central figure in the original series, so it's likely he'd be involved in this fanfic in some capacity, perhaps as the hitman or someone related to the hitman - style plot.
Obviously, Harry Potter himself would be one of the main characters. He's the hero of the original series and his story would likely continue in this fanfic.
Harry Potter himself could be a main character. He has a history of standing up against injustice, so it's likely he'd be involved in a revolt. Hermione would also be a key figure. Her intelligence and knowledge of the wizarding world's laws would be invaluable in planning and leading a revolt. Ron, with his loyalty and courage, would be right there with them.
Obviously, the illithid would be a main character. It could be a mysterious and powerful being that Harry encounters. Also, Hermione and Ron might still be important characters. They could be either suspicious of the illithid or try to help Harry understand it better. Dumbledore might also play a role, perhaps guiding Harry in his interactions with this strange new creature.
Most likely the children of the main characters from the original series. Like James, Albus, and Lily Potter. Also, the kids of Ron and Hermione, like Rose and Hugo.
Voldemort would remain a major character. Harry's new abilities and perspective from being raised by Death would make their conflict even more complex. Harry might approach the fight against Voldemort with a different strategy, one that is influenced by the teachings of Death.
Obviously, Harry Potter would be one of the main characters. He brings his own story, skills, and personality from the Harry Potter series. And Rias Gremory would also be a main character as she is from her own universe. Her leadership and unique abilities would play a major role. Hermione and Ron could also potentially be main characters as they are Harry's closest friends. In the Rias Gremory side, her peerage members like Akeno or Koneko might also be important characters in the fanfic.
Obviously, Harry Potter himself. And since he's the son of Boreas, there might be some sort of representation of Boreas, perhaps in the form of a spirit or a mentor figure who guides Harry in using his powers.
Obviously, Harry Potter would still be one of the main characters. Since it's about second chances, he might be dealing with things he didn't get to do right the first time. Hermione Granger would also be a key character as she's always been resourceful and could play a big role in making the most of these second chances. Ron Weasley too, as he's Harry's best friend. And perhaps some characters who were on the fringes in the original, like Luna Lovegood, could step into more prominent roles this time around.
Obviously, Harry Potter himself would be one of the main characters. He's always at the center of things at Hogwarts. Hermione Granger would also be a main character as she is Harry's friend and is very intelligent, she would be trying to solve the problems during the lockdown. Ron Weasley too, as he's part of the trio. And of course, Professor Dumbledore, who would be in charge of handling the lockdown situation and making decisions for the safety of the students and the school.