Well, it could be that Harry Potter, as the Master of Death, arrives in Asgard. He might use his unique magical abilities to interact with the Asgardian magic system. Maybe he'd help Asgard in some sort of crisis, like fending off a new and powerful enemy. His knowledge of the Deathly Hallows could give him an edge in dealing with threats that are even beyond what the Asgardians are used to.
A great plot for such a fanfiction would be that the Asgardians initially mistake Harry Potter for a threat because of his title as Master of Death. But as they get to know him, they realize that he can be a great ally. Harry could learn about Asgardian magic and combine it with his own Deathly Hallows - based powers. For example, he could use his knowledge of the Elder Wand to enhance the power of an Asgardian weapon. This would lead to a series of adventures where Harry Potter helps Asgard while also learning about their culture and magic.
He could interact with Thor. Harry might show Thor his Elder Wand and Thor could be impressed by its power. They could then team up for a battle against a common enemy, with Harry using his magic and Thor his hammer.
One possible fanfic could involve Harry Potter, with his newfound status as the Master of Death, being transported to Asgard. He might use his skills and powers to face the challenges there. For example, his ability to master death could give him an edge in battles against Asgardian foes. Maybe he'd form an alliance with Thor, and together they'd fight against a common enemy like Loki who has some new, more dangerous scheme.
First, Harry would need to prove himself. As the Master of Death, he has a certain aura about him. In Asgard, he could start by saving a village from a monster attack. His ability to speak with snakes (if he still has that Parseltongue ability) might come in handy when dealing with some of the more mysterious creatures in Asgard. He could also use his experience from the wizarding world's wars to strategize against Asgard's enemies. As he gains more and more respect, he becomes a hero, and the Asgardians might start to see him as a protector, like they do with Thor.
Well, Harry could find that his Deathly Hallows are perceived very differently in Asgard. His Invisibility Cloak might be seen as a powerful magical artifact like the ones in Asgard. His Resurrection Stone could be a source of great fascination as Asgardians have their own beliefs about the afterlife. And his Elder Wand might be seen as a weapon of great power, perhaps on par with Mjolnir.
In this fanfiction concept, the story could unfold in many ways. Maybe Harry would be a powerful wizard in an ancient magical society, facing different dark forces. For example, instead of Voldemort, he might battle an ancient evil sorcerer who wants to control all magic. The magic in ancient times could be more raw and less regulated, so Harry would have to adapt quickly.
The story could start with a magical accident that transports Harry Potter into the Avengers' universe. Since he's immortal, he has an edge. He could quickly learn about the Avengers and their mission. He might use his magic to save a member of the team, thus earning their trust. For instance, if Iron Man was in a life - threatening situation, Harry could use a levitation spell to get him to safety.
Well, if Harry Potter was raised by Zeref, it would be a very different story. Zeref is a rather dark and complex character from Fairy Tail. Harry might grow up with a different view of magic. He could be more inclined towards darker forms of magic or have a more cynical view of the wizarding world. Maybe he would be more isolated as Zeref's influence might not be well - received in the Hogwarts environment.
The story could be amazing. Since Narnia has a different magic system than the wizarding world in Harry Potter. Harry might have to adapt quickly. He could make friends with the talking animals in Narnia. His upbringing there would probably give him a different perspective on magic and power. For example, the power of Aslan is more like a divine power compared to the magic in the wizarding world. This could lead to some interesting conflicts or collaborations when he discovers his own wizarding heritage later.
Some Asgardians might be curious about this strange boy with a different kind of magic. Loki, for example, might see him as a potential tool or an interesting oddity to play with.