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.
In the 'Harry Potter 19 Years Later Fanfic', the main characters are bound to be the offspring of the beloved characters we know. The Potter children are obvious candidates. James could be the adventurous one, Albus the more introspective, and Lily the spunky one. Then there are the Weasley - Granger kids. Rose might be the brilliant one following in her mother's footsteps, and Hugo could be the laid - back but talented wizard. There could also be other students at Hogwarts who become important as the story unfolds, perhaps a mysterious transfer student or a child from a family that was on the fringes of the wizarding war.
The main characters would probably be the next - generation witches and wizards. Besides the Potter and Weasley - Granger children, there could be new characters introduced who are friends or rivals of them. They would be at the center of the story, dealing with their own personal growth, friendships, and rivalries just like their parents did. And of course, the original characters like Harry, Ron, and Hermione might still make appearances to offer guidance or be part of some important events in the story.
Obviously, Harry Potter himself would be one of the main characters. And the first - years he's raising, though they might be a group of nameless first - years at first, some of them could emerge as more prominent characters as the story progresses.
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.
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.
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.
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.
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.
Another possibility is that new characters might be created specifically for this fanfic. These characters could be hybrids of the two universes, having traits from both the Toaru series and Harry Potter. They could be students at Hogwarts who also possess esper abilities, or wizards who are involved in the affairs of the Toaru series' world. This would add a fresh and unique element to the fanfic.
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 himself. And then there would be the goblins. Maybe Griphook, as he was one of the more well - known goblins in the original series. He could be one of the main trainers of Harry.
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.