A cool plot could be that Thanos discovers the magical world of Harry Potter and decides to collect the Deathly Hallows as well as the Infinity Stones. The Hogwarts students and the Avengers then have to race against time to stop him. The students could use their knowledge of spells and potions, while the Avengers use their superpowers and advanced weaponry. This would create a really interesting dynamic between the two groups as they try to outwit Thanos.
Perhaps the wizards from Harry Potter could teach the Avengers some magic. For example, Harry could show them how to use the Patronus charm for protection. In return, the Avengers could introduce the wizards to their high - tech gadgets. Iron Man could be especially interested in the magical properties of things like the Elder Wand. And then there could be a big battle where the combined powers of magic and technology are used to fight off a new, powerful enemy.
Maybe the Time Stone from the Avengers universe gets accidentally sent to the Harry Potter world. This causes chaos as different characters try to use it for their own purposes. Harry and his friends might think it could be used to defeat Voldemort once and for all, while the Avengers are desperate to get it back to prevent time - related disasters in their own universe. Hermione would be very intrigued by the science behind the Time Stone and try to study it, which could lead to some interesting interactions with the science - minded Avengers like Bruce Banner.
One idea could be that Voldemort teams up with a powerful Marvel villain like Thanos. This would force the Avengers and the Harry Potter characters to join forces. The Avengers could bring their strength and high - tech weapons, while the Harry Potter characters use their magic. Another plot could be that a magical artifact from the Harry Potter world is lost in the Marvel universe and both groups have to search for it. Maybe it has the power to destroy both universes if misused.
One idea could be that Voldemort somehow makes an alliance with Loki. The Avengers would then have to team up with Harry, Hermione and Ron to stop them. They could combine magic and superpowers in battles. For example, Iron Man could use his technology to analyze and counter some of the dark magic spells while Harry uses his Patronus to protect the group from Loki's illusions.
One idea could be that the Avengers are transported to the wizarding world. Iron Man could be fascinated by the magic technology and try to incorporate it into his suit. Another could be that Voldemort somehow gets hold of the Infinity Stones and the Avengers have to team up with Harry Potter and his friends to stop him. Maybe Thor's hammer could be enchanted by a Hogwarts spell to have new powers.
One idea could be that Voldemort teams up with a villain from the Avengers universe, like Loki. This would force the heroes from both worlds to join forces. The Avengers could use their high - tech weapons and superpowers, while the Harry Potter characters would bring their magic to the fight.
One idea could be that the Avengers are somehow transported to the wizarding world. They might be initially confused by the magic but then start to work with the Hogwarts students and teachers to fight a common enemy, like a dark wizard who has also harnessed some sort of Muggle - like technology to become even more powerful. For example, Voldemort could team up with Hydra remnants to create a super - weapon that threatens both the magical and non - magical worlds.
One idea could be that Harry uses his magic to help the Avengers in a battle against an otherworldly threat. For example, he could create magical shields to protect the team or use spells to disorient the enemy. Another idea is that the Avengers visit Hogwarts and learn about the magical world. Tony Stark might be fascinated by the magic technology and try to find a way to combine it with his own inventions.
A plot might involve the Time Stone. Doctor Strange could accidentally open a portal to the Harry Potter universe. The Death Eaters, seeing an opportunity, try to steal the Time Stone. The Avengers and the Hogwarts students then have to work together. Thor could use his hammer to fight off Dementors, and Harry could show the Avengers how to use Patronuses. In the end, they manage to protect the Time Stone and close the portal.
Maybe the Infinity Stones are scattered across the Harry Potter universe. The Avengers have to team up with Harry Potter and his friends to retrieve them. During this adventure, a love triangle or rather a harem - like situation develops. For example, Harry Potter could find himself in the middle of a relationship with Pepper Potts and Ginny Weasley. They would all need to work together to stop a new dark force that is attracted to the power of the Stones.
One idea could be that Voldemort teams up with Loki. They both have a thirst for power and chaos. The Avengers and the wizards from Harry Potter's world would have to put aside their differences to fight this new, powerful alliance. Maybe the Time Stone could be involved, with Doctor Strange and Hermione trying to figure out how to use it to prevent the villains from achieving their goals.