It could be due to a cross - over event. Suppose there was a rift in the fabric of different fictional universes. Harry Potter, being in the wrong place at the right time, stumbles upon Thor's hammer. And because he has a pure heart (which is often a requirement to lift Mjolnir), he is able to pick it up and wield it, much to the shock of both the wizarding community and the Asgardians.
Perhaps a powerful wizard or a god from another realm decides to test Harry Potter. They place Thor's hammer in his path, knowing that he has the potential for great heroism. Harry, not fully understanding what he's getting into, attempts to pick it up. And due to his strong sense of justice and his courage in the face of great danger, he meets the criteria to lift Mjolnir and thus wields it, creating a whole new adventure for himself.
Fanfiction often takes creative liberties. It could be that there is a cross - over event that changes the nature of Thor's hammer's worthiness test. Maybe a powerful magical entity in the Harry Potter universe meddles with the hammer's magic. Harry Potter has shown great moral fiber throughout his adventures. His ability to love deeply, his sense of justice, and his unwavering determination against evil could be seen as the 'worthiness' factor by the hammer's magic, allowing him to lift it.
One way this could work in fanfiction is if there is some sort of cross - over event that changes the fundamental rules. For example, a powerful wizard or entity in the Harry Potter universe creates a spell that links the two different concepts of magic. Harry, being the main character, is the one to test it out. He approaches Thor's hammer with a combination of his natural magical ability and this new spell - created connection. His strong will and determination, which he has shown throughout his adventures in Hogwarts, could be the key factor that allows him to lift the hammer.
The story would be different as Harry would have a new weapon. His combat approach would change. Instead of relying solely on spells, he could use Yamato for close - range combat. This would add a new layer of action to the story.
He would become extremely powerful. Thor's hammer gives the wielder the power of Thor, which includes super strength, the ability to control lightning, and flight. Harry could use these powers to fight against Voldemort in a whole new way. He could zap the Death Eaters with lightning bolts and smash through their defenses with the hammer's strength.
When Harry Potter picks up Thor's hammer in fanfiction, the story might start with a great shock among those around him. His friends at Hogwarts would be in awe. Then, he could start exploring the powers of the hammer. As he does so, he may discover that there are certain tasks or quests he needs to complete. These could be related to either the Harry Potter universe or the Thor universe. For example, he might need to use the hammer to retrieve a powerful magical artifact that has been lost in the Asgardian realm. This would lead to a series of adventures and challenges that would shape the story.
Well, in fanfiction, the rules can be bent. Maybe it's because Hermione has a purity of heart and strong will, similar to what's required to lift Mjolnir in the original Thor lore. Fanfic writers often play with the concepts of different universes colliding, so her magic and intelligence could combine in a way that gives her the 'worthiness' to lift the hammer.
One possibility could be through some sort of magical or other - worldly intervention. Maybe a powerful magic user in the Harry Potter universe, like Albus Dumbledore, unknowingly creates a rift that connects the Asgardian realm to the wizarding world. And through this rift, some sort of strange magic causes Thor and Loki's essence to combine with a human, resulting in Harry being born. However, this would be a very convoluted and out - of - the - box explanation.
He would gain Thor - like powers. Just as Thor can control lightning and has super strength, Harry might be able to access similar powers. He could use the hammer to fly and fight against enemies in a more powerful way than he could with just his wand.
One implication is that it shows the universality of certain values. If Harry can lift the hammer, it means his qualities like courage and selflessness are recognized across different fictional universes. It also blurs the lines between the two worlds of magic, making for interesting crossovers in the story.
Well, if Harry Potter were to pick up Thor's hammer in fanfiction, he might find himself suddenly connected to the power of Thor. It could be that his magic somehow complements the magic or power within the hammer. He could use it to fight against the dark forces in his own world or be drawn into adventures in the realm of Thor. It would be a really cool crossover concept, and it might also cause a stir among the wizards in the Harry Potter world who would be both amazed and perhaps a bit envious.