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 Avengers are on a mission when they are suddenly transported to Hogwarts. There, they find out that a new dark force, created by a combination of dark magic and Hydra experiments, is emerging. Harry, Ron, and Hermione join forces with the Avengers. Captain America's leadership skills help organize the Hogwarts students for battle. Hulk could be used as a powerful weapon against the dark creatures, and the wizards' magic could assist the Avengers in taking on the high - tech threats of Hydra - related enemies.
One possible plot could be that Voldemort teams up with Loki. The Avengers and the Hogwarts crew would then have to work together. Harry, with his knowledge of magic, could teach the Avengers some basic spells to counter the dark magic Voldemort and Loki are using. Iron Man could use his technology to enhance some of the Hogwarts defenses. And Thor could share his knowledge of Asgardian magic with the wizards at Hogwarts.
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 interesting plot point is the clash of magic and technology. In many crossovers, the Avengers are used to high - tech gadgets, while the Harry Potter world is full of magic. Seeing how they interact with each other, like Iron Man trying to reverse - engineer a magic spell or Hermione trying to understand the science behind the Avengers' equipment, is really fascinating.
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.
The Stargate could be a portal between different magical realms in the Harry Potter universe. For example, it could lead to a place where ancient and more powerful magic exists. Wizards from different schools around the world could team up with Stargate explorers to uncover the secrets of this new place. There might be a new threat emerging from this realm that requires both magic and Stargate technology to defeat. This would bring together characters like Harry Potter and Jack O'Neill to lead the charge against the common enemy.
Well, perhaps there's a rift in the multiverse that connects Central City to Hogwarts. The Flash, while chasing a villain, gets sucked into the wizarding world. Harry Potter and his friends initially suspect him as a threat but then realize his good intentions. They then combine their powers - the Flash's speed and the magic of the wizards - to fight a common enemy. For example, the Flash could use his speed to distribute protective spells all over Hogwarts really quickly, while Harry and his friends focus on the offensive magic against the bad guys.
One idea could be that Carly and her friends discover a magical portal in their apartment that leads to Hogwarts. They then have to navigate the wizarding world, with Carly being fascinated by all the magic. Meanwhile, Harry Potter and his friends are intrigued by the strange Muggle - like devices the iCarly gang has. They end up teaming up to solve a mystery that involves both the wizarding and Muggle worlds.
Well, perhaps the Death Note from the Bleach universe gets mixed up with the magic in Harry Potter's world. A powerful wizard could get hold of it and start using it in ways that disrupt the balance of life and death in both worlds. Harry and his friends would have to figure out how to stop this misuse, with the help of some Bleach characters who understand the true nature of the Death Note.
One idea could be that Eragon, while on one of his adventures in Alagaësia, accidentally creates a portal that leads him to Hogwarts. There, he meets Harry Potter and they quickly realize they have a lot in common. They could team up to fight against a dark force that somehow threatens both their worlds, like a new type of dark magic that combines the magic of Alagaësia and the dark arts from the wizarding world.