One way is through a portal - type situation. A magical portal could open up between the two worlds, and characters from each side could cross over. Harry Potter characters might find themselves in Dunwall and have to use their magic in a new, more dangerous environment. Dishonored characters in Hogwarts could be amazed by the magical creatures and spells, and they could all form alliances based on their shared goals, like fighting against dark forces in both worlds.
You can combine them by having their abilities merge. For example, a Hogwarts student could learn to use Corvo's powers of possession. They could then use this to possess animals or even other students to solve mysteries or get out of tricky situations at school.
The characters can be combined through a magical accident. For instance, a spell gone wrong could transport some Storm characters to Hogwarts or vice versa. Then they would have to figure out how to work together. Harry could teach Storm characters about magic, and Storm characters could show Harry and his friends about their powers.
A prophecy could be written in the fanfiction that ties their fates together. So, they are forced to interact and rely on each other's skills. Kalona's strength and Harry's knowledge of magic could complement each other in fulfilling the prophecy.
The characters can be combined by creating scenarios where they meet. For example, a magical portal could open between Hogwarts and a Star Wars planet. Then, characters like Harry Potter might be attracted to the unique qualities of characters like Princess Leia or Luke Skywalker, forming part of a harem. Or a Sith Lord could find the magic of the Harry Potter world fascinating and start to court some of the powerful witches or wizards there.
They can be combined by having their skillsets merge. For instance, Harry's ability to use magic like the Patronus charm could be used to protect Bond during a dangerous mission. Bond's expertise in driving fast cars and using high - tech gadgets could assist Harry in escaping from Death Eaters in a Muggle - filled area.
The settings can also be combined. Picture a scenario where the Forbidden Forest in Hogwarts is used as a training ground by Kakashi for the students. He could set up ninja - like obstacle courses among the magical trees and dangerous creatures. This would bring a whole new dimension to the Hogwarts experience.
Another way is to create a crossover where the worlds of Naruto (where the Mangekyou Sharingan comes from) and Harry Potter collide. In this scenario, the rules of both universes would have to be adjusted. For instance, the magic in Harry Potter could interact with the chakra system of Naruto. A character with the Mangekyou Sharingan could use it to detect hidden magical spells or even use their Sharingan - based abilities in magical duels, adding a new dimension to the battles in the Harry Potter world.
The worlds can be combined by having characters cross over. For instance, Superman could be called to Hogwarts to help deal with a dark wizard who has powers that are beyond the normal magical abilities. His invulnerability would be a great asset in battles against dark magic.
One way is through magical items. For instance, a magical object from the Harry Potter world like the Philosopher's Stone could end up in Tinkerbell's world and she has to protect it from the dark fairies. Or vice versa, a fairy magic item could find its way into Hogwarts and cause a stir.
They can be combined by making the Black Mamba a part of the magical creatures in the 'Harry Potter' universe. For example, it could be a new kind of Animagus form.
One way to combine them creatively is by having an Avatar character attend Hogwarts. Imagine an Airbender learning magic, using their airbending skills to enhance their spell - casting, like using air currents to direct a spell more accurately. Another idea could be a crossover where the Avatar world's spirits interact with the magical creatures in the Harry Potter universe. For example, a Patronus could be seen as a form of spirit energy, and perhaps there could be some kind of connection or interaction between them.