One possible plot could be that Batman finds himself in the wizarding world of Harry Potter. He could use his detective skills to solve some magical mysteries that even the wizards are having trouble with, like a series of unexplained disappearances in Hogwarts. Maybe he teams up with Harry Potter and his friends, and Batman teaches them some non - magical self - defense techniques in return for learning about magic from them.
A crossover plot could center around a new villain who has the ability to travel between the magical and non - magical worlds. This villain starts causing chaos in both Gotham and the wizarding world. Batman and Harry Potter must put aside their differences in methods (magic vs non - magic) and work together. Harry could use his Patronus to protect Batman from Dementors that the villain summons in Gotham, while Batman uses his Batmobile to quickly transport Harry and his friends to different locations in the wizarding world to stop the villain's minions.
The plot might involve Voldemort getting hold of some high - tech gadgets from Gotham City. Batman then teams up with the Order of the Phoenix to stop Voldemort from using these gadgets to gain more power. Harry Potter could be fascinated by Batman's cool gadgets and try to incorporate some of the technology into the wizarding world's defenses. For example, they could create a spell - protected Bat - signal to call for help during the final battle against Voldemort.
One possible plot could be that Voldemort's dark magic starts to seep into Gotham City. Batman, being the detective he is, starts to notice strange and magical happenings. Meanwhile, Harry Potter, Ron and Hermione get transported to Gotham through a magical accident. They team up with Batman to stop Voldemort's influence from spreading further. Harry uses his magic skills and Batman uses his gadgets and combat skills to take on the Death Eaters and Gotham's villains who have been corrupted by the dark magic.
One possibility could be that in a magical world where Harry Potter exists, Batman's skills and detective abilities are overlooked. Maybe Batman is magically transported to the wizarding world and is initially dismissed as just a Muggle with no real value. But he starts using his gadgets and his sharp mind to solve mysteries that even the wizards can't figure out, like a series of strange disappearances in Hogwarts that are related to some dark magic - Muggle technology combination.
Another possibility is a scenario where Voldemort decides to expand his reach into the non - magical world and Batman becomes aware of this threat. He would then enter Hogwarts undercover to learn about magic and form an alliance with the Order of the Phoenix. The contrast between Batman's brooding, non - magical detective nature and the magical world would make for an interesting story.
One possible plot is that a dark magic from the Darksiders universe seeps into the Harry Potter world. Harry and his friends discover that the only way to stop it is to learn some secrets from the Darksiders. So they embark on a journey through both worlds, meeting various characters from each along the way and using a combination of magic and the powers of the Darksiders to combat the threat.
The plot could involve Maleficent's magic interfering with Hogwarts' protective spells. She might be on a quest to find a powerful magical artifact hidden in Hogwarts that she believes will make her even more powerful. Harry and his friends suspect her motives and start to investigate. In the process, they learn about Maleficent's past and find some similarities between her story and their own fight against the dark forces in their world.
Well, it could be that Supergirl lands in the wizarding world somehow. Maybe she's chasing a bad guy who uses magic to escape to Hogwarts. And then she teams up with Harry Potter to fight the bad guy. Harry could teach her about magic while she teaches him about her superpowers.
Well, perhaps the magical creatures from the Harry Potter universe end up in the '300' setting. Dragons could be used by the Spartans to fight their enemies. The centaurs could also join the battle, lending their archery skills. And Harry could learn some combat skills from the Spartans, which he could then use back in the wizarding world to fight Voldemort's Death Eaters.
One possible plot could be that Moana's island is threatened by dark magic from the Harry Potter universe. Harry, Hermione, and Ron could be transported to Moana's world while on a mission to stop the spread of this dark magic. They would team up with Moana to use her knowledge of the ocean and the island's magic, along with their own wizarding skills, to fight off the dark forces. Maybe they'd have to face off against a wizard who has enchanted some of the sea monsters in Moana's world.
One possible plot could be that the Flash accidentally runs into the wizarding world. He might be chasing a villain who has some sort of magic - based powers and ends up in Hogwarts. Harry Potter and his friends could be initially suspicious of this strange, super - fast man in a red suit. But then they realize they can work together. The Flash could use his speed to help in tasks like quickly gathering potion ingredients across the vast Hogwarts grounds, while Harry and his friends could use magic to help the Flash understand and navigate the complex magical world.
One possible plot could be that Aquaman somehow finds himself in the wizarding world of Harry Potter. Maybe a magical spell gone wrong transports him there. He could use his unique underwater abilities to help the Hogwarts students in a task related to the Black Lake, like retrieving a powerful magical artifact that has sunk to the bottom.