In a Harry Potter Darksiders crossover fanfiction, perhaps Voldemort somehow makes a pact with the forces of the Darksiders. This forces the protagonists of the Harry Potter series to not only fight against Voldemort but also the additional threats from the Darksiders world. The characters from both universes would have to overcome their differences, like the wizards having to understand the more brutal and otherworldly powers of the Darksiders, while the Darksiders might have to get used to the complex magic system of the wizarding world.
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.
In a Naruto and Darksiders crossover fanfiction, there are numerous possibilities. For starters, the art of ninjutsu could be seen as a new form of power in the Darksiders' universe. Naruto's ability to befriend his enemies might also play a role. He could try to reason with some of the more morally ambiguous characters in Darksiders. On the other hand, the Darksiders' characters could introduce Naruto to a whole new level of power and danger. Their weapons and abilities are far different from what he's used to in Konoha. This could lead to Naruto growing in new and unexpected ways, perhaps even unlocking new forms of his own power.
In a Harry Potter and Superman crossover fanfiction, perhaps Voldemort discovers Superman's existence and tries to use his powers for his own evil deeds. He might try to control Superman's mind. But Superman, being the strong - willed hero he is, resists. Harry and his friends then team up with Superman to fight Voldemort. They learn a lot from each other. Harry learns about physical strength beyond magic, and Superman gets to understand the complexity of magic.
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.
Well, one possibility could be that Godzilla somehow ends up in the wizarding world. Maybe a powerful dark magic spell goes wrong and creates a portal that sucks Godzilla in. Harry and his friends at first think it's a new kind of dark creature created by Voldemort. They try to fight it using spells, but soon realize that Godzilla is not exactly evil. Godzilla might then start causing destruction in Hogwarts, and the wizards have to figure out a way to either send it back or control it without killing it.
Hermione and Death could be an interesting pairing. Hermione is known for her intelligence and thirst for knowledge. Death, being an all - powerful entity in the Darksiders universe, could have a lot of knowledge that Hermione would be eager to learn. Their conversations would likely be deep and thought - provoking as she tries to understand the nature of death from his perspective.