One way it could work is by having the magical elements of Harry Potter in the Justice League universe. For example, the wizards could help the Justice League with their spells in battles against powerful foes. Maybe Harry Potter himself could use his Patronus charm to fend off some of the League's enemies like Darkseid's minions.
It could also be interesting if the Justice League members visited Hogwarts. Superman might be seen as a sort of super - wizard by the students. Batman could use his detective skills to solve some of the mysteries in the wizarding world, like the secrets of the Chamber of Secrets. And Wonder Woman could show off her combat skills and inspire the young witches and wizards to be brave in the face of danger.
Another concept is that the magic from the Harry Potter series starts to seep into the DC universe where the Justice League operates. This causes chaos as the laws of physics in the DC world are disrupted. The Justice League has to seek help from Hogwarts professors to understand and contain this new form of magic energy. Superman might be intrigued by the idea of magic being a new power source or a new threat he can't easily overcome with his super strength.
Imagine a scenario where a young wizard from the Harry Potter world, who has a natural ability to open portals, accidentally opens a gateway to the world of the Justice League. However, this also attracts the attention of Silent Hill. The League and the wizards have to work together to close the portals and keep Silent Hill's nightmares at bay. The wizards can use their spells and the League can use their superpowers to fend off the encroaching darkness.
It could be a wild and exciting story. Maybe the wizards from Harry Potter team up with the super - heroes of the Justice League. The immortals in the story could be Dumbledore or Voldemort from Harry Potter world, and they bring their magic to the Justice League's fight against evil. It would be a clash of different powers and cultures.
If we consider the harem aspect first, perhaps there's a powerful character who has the ability to draw characters from both the Justice League and Harry Potter series into their 'harem'. The 'lemon' could be part of a magical or scientific experiment that links these two disparate universes. For instance, it could be a lemon - shaped device that opens portals between the two worlds. And in this new combined world, the characters have to navigate their relationships and powers while dealing with the challenges that come with this strange new setup.
One way it could work is by having the magical elements of Harry Potter blend with the anti - hero nature of the Suicide Squad. For example, the Suicide Squad could be sent on a mission in the wizarding world. They might have to deal with dark wizards or magical creatures. Their non - magical weapons and skills could be pitted against magic, creating an interesting dynamic.
In fanfiction, the characters could interact during a global crisis. Let's say an ancient evil is rising that combines magic and advanced technology. The Justice League realizes they need the help of the wizards from Harry Potter's world. So, they send representatives like Superman and Wonder Woman to Hogwarts. There, they meet Dumbledore and the students. The students are excited to see these super - heroes and together they form a plan to fight the evil. They combine the super - powers of the Justice League with the magic of Hogwarts to defeat the enemy.
He could be a valuable asset. His immortality means he has a vast amount of experience. He could use his magic to heal the injured members of the League quickly. For instance, with a spell like 'Episkey', he could mend wounds in seconds.
One idea could be that the Shinju's power somehow connects the Naruto universe and the Justice League's universe. Maybe the Shinju's energy creates a rift, and Naruto characters end up in the Justice League's world. They could team up to fight a common enemy that is attracted by the strange energy of the Shinju. For example, a powerful demon from Naruto's world could be drawn to the new universe and the Justice League, with their high - tech and superpowers, join forces with Naruto and his friends who have ninja skills and chakra abilities.
Another possibility is a post - Endgame fanfiction. After the events of Endgame, the Avengers discover a new threat that has ties to the Justice League's world. Maybe a powerful villain from the DC universe has somehow been awakened by the events in the Marvel universe. So they have to reach out to the Justice League for help and together they figure out a way to stop this new threat.
One idea could be a crossover where Goku is accidentally transported to the Justice League's universe. He might initially be seen as a threat due to his power but then they realize he's a good - hearted fighter. They could team up to fight a common enemy like Darkseid who has somehow acquired the Dragon Balls and is using them for his evil plans.