Perhaps 'y' is a relative of Harry's that was thought to be dead. This relative could have a unique magical heritage that they pass on to Harry, making him even more powerful. For example, if 'y' was a distant cousin from a line of powerful seers, Harry might develop some precognitive abilities.
It's hard to say without reading it. It could be the original characters like Harry, Hermione, and Ron if it's a continuation of their story. Or it might focus on new characters created by the fanfic author.
It's hard to say for sure without reading it, but it's likely that Harry Potter would still be one of the main characters since it's a Harry Potter fanfiction. He might be portrayed in a different light, though.
One possible plotline could be that the character 'y' imparts unique magical knowledge to Harry. For example, 'y' might teach Harry a different form of magic not taught at Hogwarts, like an ancient and almost forgotten spellcasting method. This could give Harry an edge in his battles against Voldemort.
Harry Potter himself is likely to still be a main character. He's the face of the series. Hermione and Ron will probably also be important. But new characters might be introduced too, perhaps a mysterious new student or a powerful wizard from a far - off land.
One reason to start questioning Harry Potter fanfiction could be the divergence from the original lore. Some fanfictions might change key aspects of the wizarding world, like magic rules or character personalities. For example, if a fanfiction makes Harry a completely different person with no regard for his canon traits, it can be off - putting.
It could also be due to the fact that a large portion of fanfiction focuses on shipping (pairing characters romantically). While shipping can be fun for some, others might feel that it overshadows other aspects of the story. For example, if most fanfictions are just about who Harry should be with instead of exploring the rich magical world further, it can make you question its overall popularity.
Perhaps you could start with 'Was Snape truly redeemed? And did Harry ever fully understand his sacrifices?' These two questions can lead to a deep exploration of the complex relationship between Harry and Snape, delving into the moral and emotional aspects of the story. It can create a fanfiction that focuses on the gray areas of the characters' personalities and actions.
There could be a new professor at Hogwarts. Maybe a young and brilliant wizard who has just returned from a long journey in a far - away magical land. This professor could bring in new ideas and spells, and become an important figure in Harry's new path.