Sometimes, even the villains like Voldemort or his Death Eaters play important roles. Harry could read their minds to gain an upper hand, and they, in turn, might try to find ways to block Harry's power or use it against him.
Ron could also be there. He might be in charge of something like the Gryffindor Quidditch team or be a part - time teacher teaching the younger students about the magical history of the Weasley family's inventions. His humor and loyalty would be a great addition to the story.
Obviously, Harry Potter himself is often a central character. His friends like Hermione Granger and Ron Weasley also frequently appear. In some fanfictions, they might play different roles compared to the original books. For example, Hermione could be the one who stumbles upon a dark secret first and has to convince Harry and Ron to take action.
Harry Potter himself is often involved. He might be the one to encounter the first signs of inflation, whether it's a magically inflating potion or an enchanted object. His friends, like Ron and Hermione, are also likely to be part of the story, helping him figure out what's going on.
Ron Weasley could also be a key figure. He might be Harry's loyal friend as always, standing by his side during all the changes that Harry is bringing about in the wizarding world as a god. And there could be new characters introduced as well, perhaps other gods or magical beings that interact with Harry in this new fanfiction realm.
In some cases, Albus Dumbledore could play an important role. His wisdom and power in the wizarding world would make him a key figure in any situation where the two different universes collide. He might be the one to first discover Alexstrasza's presence and figure out how to make use of her abilities in the fight against the dark forces in the Harry Potter world.
Obviously, Harry Potter himself is always a main character. He is the one most directly associated with the concept of death in the original series, what with his parents' death and his multiple near - death experiences.
Ron Weasley could be another main character. He might be initially skeptical about the piano's magic but then be amazed when he sees the extraordinary things it can do. Maybe he accidentally discovers a new function of the piano while fooling around with it in the Gryffindor common room.
Harry Potter himself could be one of the main characters in such fanfiction. Maybe he gets an automail limb after a particularly dangerous encounter with Voldemort. Hermione might also be involved, using her vast knowledge to help understand and improve the automail technology within the wizarding context.
Obviously, Harry Potter himself is a central character even though he's thought to be dead. His best friends like Hermione and Ron are usually major characters as they would be the ones most likely to try and find out what really happened or bring him back.
In addition to Harry, there could be other important characters such as Sinestro. Sinestro could initially be an antagonist, seeing Harry as an outsider in the Green Lantern world and trying to undermine him. But as the story progresses, their relationship could become more complex. There might also be the Guardians of the Universe who play a role in guiding Harry in his new role as a Green Lantern.