Well, it depends on the creativity of the fanfiction writer. He could potentially meet his deceased parents or other long - lost relatives. Maybe he discovers a hidden power within himself that the mirror unlocks, which then leads him on a new adventure to defeat Voldemort in a completely different way than in the original story.
In some fanfictions, when Harry Potter goes through the mirror, he might find himself in a parallel magical world. This world could have different versions of his friends and enemies, and he may have to face new challenges to find his way back to his own world.
When Harry goes through the mirror in fanfiction, he may enter a time - altered realm. Here, the past, present, and future are all jumbled up. He could interact with his past self, change certain events, and as a result, change the entire course of the wizarding world's history. For example, he might prevent some of Voldemort's early dark deeds, which would have a huge impact on the present and future of the wizarding community.
He might encounter some strange magical creatures that are only found underground. For example, there could be a new type of goblin or a magical mole with special powers.
He could encounter a new magical creature. The goblins at Gringotts are known to have various magical creatures guarding different vaults. Maybe Harry comes across a rare and friendly creature that helps him on his journey. For example, a small fire - breathing dragon that he befriends and it later aids him in a battle against Voldemort's forces.
He might meet some strange magical creatures there that are used for experimental treatments.
In the fanfiction, Snape could be in a really tough situation when Harry comes to him for help. On one hand, he has his loyalty to the Dark Lord (or at least that's what others think), and on the other, there's this boy who is the son of the woman he loved. He might end up guiding Harry in a very roundabout way, like giving him a potion ingredient that has a hidden meaning or leading him to a certain book in the library that contains the solution to Harry's problem.
In the 'Harry goes through the veil fanfiction', Harry may face a great deal of danger. The veil is often associated with death in the wizarding world. So, perhaps he has to fight off dark forces that lurk on the other side. He might also have to find a way back to the living world, which could involve solving puzzles or making difficult choices. There could be a new set of magical rules there that he has to learn quickly in order to survive.
In fanfic, when Harry Potter goes to Gringotts, he might discover some long - lost secrets about his family's vault. There could be hidden spells or artifacts that were left there by his parents or ancestors.
Maybe Harry has some strange magical illness that normal wizards can't cure. So he has to seek help from a very special doctor who might have some unique remedies.
Perhaps he would be seen as an oddity at Alfea. After all, he comes from a completely different magical system. But his reputation as the 'Boy Who Lived' might precede him. Some might be in awe of him, while others might be skeptical. His presence could also stir up some rivalries among the students at Alfea who are used to their own hierarchies. Harry would have to find his place among the fairies and deal with any potential jealousies or hostilities.
Well, he might encounter new magical creatures unique to America, like the Thunderbird. He could also visit American wizarding schools and be amazed by their different teaching methods compared to Hogwarts.
In this fanfiction, Harry could attend a Canadian wizarding school. He'd have to adapt to a different teaching style and make new friends. The curriculum might include courses on Canadian magical history and spells that are specific to the region. He might also face some challenges from local wizards who are not used to having a famous wizard like him around.