One idea could be a crossover where Doctor Strange uses his magic to visit the wizarding world of Harry Potter. He could meet Harry and help him with some of his more difficult magical problems, like dealing with a particularly powerful dark magic spell that the Hogwarts professors are stumped by.
Another possibility is a story in which a young wizard in the Harry Potter world discovers a hidden portal that leads to the dimension where Doctor Strange operates. This wizard, inspired by Strange, begins to study a new form of magic that combines the principles of both universes. They then return to Hogwarts and start to teach their friends this new hybrid magic, which causes quite a stir among the faculty and students alike.
One possible plot could be that Doctor Strange uses his magic knowledge to train Harry in more advanced and esoteric forms of magic. Harry might learn to manipulate time and space in ways that are different from the normal Hogwarts curriculum. For example, he could learn to create stable time loops to study spells without the risk of negative consequences. This would give him an edge in his fight against Voldemort as he could plan better strategies and anticipate his enemy's moves.
One possible plot could be that Harry, as the son of Doctor Strange, discovers his magical abilities from both the wizarding world of Harry Potter and the mystic arts of Doctor Strange. He might use his combined powers to fight new and powerful dark forces that threaten both the magical and non - magical realms.
One common theme is magic exchange. For example, exploring how the magic from the Harry Potter universe would interact with the magic in Doctor Strange's world. Another theme could be character crossovers, like Harry meeting Doctor Strange and learning from him or vice versa.
A possible plot could involve a new, powerful dark sorcerer who has found a way to combine magic from both universes to become invincible. Doctor Strange tries to stop him but is quickly overpowered. Meanwhile, Harry Potter senses the danger through his connection to magic. He travels to Doctor Strange's side. Harry uses his knowledge of magical creatures from the Forbidden Forest. He summons a group of Centaurs who help him in the battle. With their combined strength and Harry's strategic use of spells like the Stunning Spell, they are able to defeat the dark sorcerer and save Doctor Strange.
In a fanfiction scenario, it could be that the Time Stone has some sort of connection to the magic in the Harry Potter world. Doctor Strange is in trouble while dealing with an enemy who wants to misuse the Time Stone. Harry Potter, with his knowledge of time - turning devices like the Time - Turner, manages to outwit the enemy and save Doctor Strange.
In such a fanfiction, Harry Potter would probably grow up with a much different set of values. Doctor Strange is often about protecting the world from threats from other dimensions. So Harry could be trained to face threats that are not just from the dark wizards in his own world. He might also have access to some really cool artifacts from the Marvel universe. And his relationships with his friends would be different too. Instead of just Hogwarts classmates, he could have allies from different realms.
In a fanfiction where Harry Potter meets Doctor Strange, the possibilities are endless. Harry, who is used to the structured magic of the wizarding world, would be fascinated by Strange's more fluid and unpredictable magic. Strange, on the other hand, would be intrigued by the hidden magical society that Harry comes from. They could exchange knowledge about different dimensions. Harry could learn about the multiverse from Strange, and Strange could gain insights into the magical dimensions that exist within the Harry Potter universe. They might also have a friendly duel to test each other's skills, which would be a spectacular display of two very different kinds of magic.
Well, Hermione could be really intrigued by Doctor Strange's library. She might ask him all sorts of questions about the books and scrolls he has, and they could exchange knowledge about different magical concepts. For example, Hermione could learn about the use of astral projection from Strange, and in return, she could teach him some of the more complex spells from the wizarding world.