Dumbledore's character often plays a role. He might be a guiding figure in the background, even if Harry is going against his wishes. And there could be new characters introduced, such as other outcast wizards or witches who Harry meets during his travels.
Obviously, Harry Potter himself is a main character. Hermione and Ron often play important roles too. They might try to break Harry out of Azkaban or help him from the outside. Sometimes, Sirius Black could also be involved, especially if the story is related to the secrets of Azkaban or the wrong imprisonments. Dumbledore could also be a key figure, guiding Harry or influencing the events from afar.
Obviously, Severus Snape is the central character. He is the one who travels back in time, so all the actions and changes are centered around him. But other important characters often include Lily Evans. Since Snape had a deep connection with her, he might try to interact with her in different ways to change the past.
Obviously, Harry himself is the central character. Hermione is also often involved as she is Harry's friend. Ron too, as they are a trio. Dumbledore usually plays an important role as he is the headmaster. Snape is also a popular character in these fanfictions as Harry might try to change their relationship. And of course, Hagrid, who is always there for Harry in the original story and could be involved in new and different ways in the fanfiction.
Well, obviously Harry Potter himself is the central character. Hermione and Ron are almost always involved too. They would be the ones trying to figure out what's wrong with Harry and how to fix him. Dumbledore might also play a major role, as he often has deep knowledge about magic and could potentially help Harry regain his sanity.
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.
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.