Maybe in the fanfic, Batman's rogues gallery somehow teams up with some of the Avengers' villains. This forces Batman and the Avengers to work together. Batman could introduce his unique gadgets and combat style to the Avengers, while they could show him their superpowers up close. For example, Iron Man could be intrigued by Batman's utility belt and try to create his own version of some of the gadgets.
A good plot could involve a villain from the Homestuck universe creating chaos in the Avengers' world. The Homestuck characters come to help, but there are misunderstandings at first between them and the Avengers. However, as they start to understand each other's powers and motives, they form a strong alliance to defeat the villain.
Another idea is that a villain creates a rift between the two universes. The Avengers and Merlin have to team up to close this rift. During their journey, they exchange skills and knowledge. Black Widow could teach Merlin some combat skills, while Merlin could show the Avengers how to use magic in a more strategic way. This way, they not only close the rift but also become stronger as a combined force.
One possibility could be that Ben Grimm, as The Thing, brings his unique strength and loyalty to the Avengers. His rocky exterior could be a great asset in battles, like providing cover for his teammates. He might also have some interesting interactions with the other Avengers, especially those with a sense of humor like Tony Stark. They could make some witty remarks about his appearance while also respecting his power.
One possible plot could be that the Avengers are somehow transported to the Arrow's universe. Maybe a villain in the Arrowverse has acquired a powerful artifact that creates portals, accidentally pulling in the Avengers. Then, they team up with Arrow and his team to fight against a common enemy, like a new super - powered threat that neither group could handle alone.
One key element is the character interaction. How Venom, with his anti - hero nature, interacts with the heroic Avengers. For example, his relationship with Spider - Man within the Avengers context can be very interesting.
One unique element is the combination of magic and superpowers. In normal stories, these are two very different concepts. But in a crossover fanfic, seeing Iron Man's tech interact with spells from Hogwarts is really cool.
One possible plot could be that Batman's Gotham is threatened by a powerful villain who has some connection to the Avengers' universe. Maybe Loki decides to cause chaos in Gotham as part of a larger plan against Earth. Batman, being the detective he is, starts to investigate and soon realizes that this is no ordinary criminal. He then somehow gets in touch with the Avengers, perhaps through SHIELD's intelligence network. Together, they combine their skills and resources to take on Loki and his minions. Batman's stealth and strategic mind would complement the Avengers' superpowers.
One idea could be to cross the Avengers with the X - Men. Imagine Wolverine and Captain America teaming up for a mission, their different leadership styles would create interesting dynamics. Another could be crossing them with the Harry Potter universe. Picture Iron Man trying to figure out how magic works in Hogwarts. Or a crossover with the Justice League, seeing Thor and Superman in a battle of strength would be epic.
Yes, 'Supernatural Hunters and the Avengers' is quite good. In this fanfic, the Avengers team up with Sam and Dean to stop a powerful dark force that is threatening both the Marvel universe and the Supernatural world. The story does a great job of combining the different mythologies of both franchises. For example, it has Thor interacting with angels in a really interesting way.