Sometimes other Hogwarts students or professors can be involved. For example, Hermione might be a friend to the sister and help her understand her magical abilities. Or Dumbledore could be a guiding figure, aware of the significance of the sister's existence even before her birth, perhaps having some knowledge about the magic related to her time in the womb.
Then there's their parents. In the fanfiction, the mother could be a key figure as the one carrying the sister in the womb. Her experiences during pregnancy might be detailed, like any strange feelings or dreams she had. And the father, who might be involved in protecting the family during this time when the sister is in the womb. Their family bond is often an important aspect in these stories.
Another important character that is often involved is Hagrid. He might be the one who stumbles upon the forgotten twin sister in her hiding place or he could be the one to introduce her to the wizarding world properly. Then there are the Weasley family members. They could play different roles, like Ginny might become the twin sister's best friend or Fred and George could include her in their pranks and adventures, adding some light - heartedness 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.
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.
Well, of course, Harry Potter himself is often the central figure. He's usually the one who discovers the amulet or is tasked with dealing with its powers or secrets. Hermione Granger also frequently appears, using her vast knowledge to help Harry understand the amulet.
Harry Potter himself is often involved. He might be the one to discover a mysterious egg or be tasked with protecting it. Hermione Granger could also be a main character, using her vast knowledge to figure out the nature of the eggs. Ron Weasley might be there too, providing some comical relief while also helping with the situation.
In some fanfictions, characters like Neville Longbottom could emerge as key figures in emancipation. After his growth and development in the original series, he could use his new - found confidence and skills to fight for the rights of those who are oppressed, whether they are house - elves, werewolves or Muggle - borns.