The plot might involve the Justice League finding a way to incorporate magic into their understanding of the world because of Harry. For example, the Flash could be curious about how Harry can apparate and might try to find a scientific explanation for it. Aquaman could teach Harry about different forms of communication, as he has his own unique way of communicating underwater. As Harry grows, he might use the Justice League's resources to fight against the Death Eaters. He could bring some of the League's technology into the wizarding world, which would change the dynamics of the fight against Voldemort.
One idea could be that the Justice League somehow ends up in the wizarding world. Maybe a magical portal opens during a battle in their universe and sucks them into Hogwarts. Superman's powers could be affected by the magic there, and Batman would be intrigued by the complex magic system and start studying it. Harry Potter and his friends could team up with the Justice League to fight a new dark force that threatens both the magical and non - magical worlds.
One idea could be that Voldemort discovers a way to enter the DC universe and teams up with some of the Justice League's villains like Lex Luthor. The Hogwarts students and the remaining members of the Justice League have to join forces to stop them. The wizards can use their magic while the superheroes use their powers.
Well, one major plot change could be his relationship with magic. In Canada, the magical community might have different traditions. Maybe the way magic is taught in Canadian wizarding schools is more nature - based compared to Hogwarts. So Harry would grow up with a different understanding of magic.
One possible plot could be Harry growing up believing he is on the right side by following Bellatrix and the Death Eaters. But then he discovers some secrets about his real parents and starts to question everything he's been taught. This leads to an internal struggle as he tries to decide whether to stay with Bellatrix or break away and find his true identity.
One possible plot could be that the Death Eaters in the Harry Potter world form an alliance with some super - villains from the Justice League universe. Harry and his friends then team up with the Justice League heroes to fight this combined evil. For example, Superman could use his super strength to take on the giants in the wizarding world while Hermione helps Batman with her vast knowledge to figure out the villains' plans.
A Harry Potter and Justice League harem fanfic could start with a portal opening between the two worlds. Characters like Harry Potter himself might find himself in the world of the Justice League, or vice versa. The harem part could play out in different ways. Maybe Superman, being the noble hero he is, finds himself in a situation where he has to protect multiple female characters from both universes. And as they spend more time together, feelings start to develop in a complex web of relationships. It would be a unique take on the crossover genre, exploring both the action - packed aspects of the Justice League and the magical elements of Harry Potter while adding the interesting dynamic of a harem.
His character would develop a more global perspective. Instead of just focusing on the wizarding world's problems, he'd be aware of the wider universe of threats that the Justice League faces. This could make him more open - minded and innovative in his approach to solving problems. He might also be more physically fit and combat - ready, having trained with Batman and others. His relationships with others would be different too. He might not have the same close - knit group of friends as in Hogwarts, but rather a more diverse group of allies from different backgrounds, like the various members of the Justice League.
In a fanfic, the coexistence could be due to a multiverse theory. The multiverse has branches that include the Harry Potter universe and the DC universe where the Justice League exists. A disruption in the multiverse causes these two universes to start overlapping. As a result, the heroes and wizards have to collaborate. They might face a threat that is using the chaos of the overlapping universes to gain power, like a dark wizard who teams up with a supervillain from the DC universe.
In a 'Harry Potter Harem Justice League Fanfiction', it could start with Harry being transported to the Justice League's universe. He discovers that his magic is a unique power there. The harem might form as the female members of the League, like Hawkgirl and Black Canary, are intrigued by this new 'wizard' in their midst. Meanwhile, they all figure out that an old enemy of the League has teamed up with Death Eaters from Harry's world. So, they train Harry in their ways and he teaches them some magic, all while dealing with the budding relationships.
In such a fanfic, Harry Potter as the Master of Death would bring a whole new dynamic to the Justice League. His magical abilities are different from the superpowers of the League members. He might have to adjust to the more scientific and modern world of the Justice League while still relying on his old magical knowledge. And the League would have to learn to work with his rather unorthodox methods.