A crossover with Harry Potter might be cool. Imagine Shadowhunters going to Hogwarts to investigate a magical disturbance that is also related to the Shadow World. The clash between magic and runes would make for an exciting story. They could also interact with the students and teachers, and there could be some interesting cultural exchanges between the two magical worlds.
One idea could be a crossover with the Vampire Diaries. Shadowhunters could team up with the Mystic Falls gang to fight a common supernatural threat, like an ancient demon that neither group can handle alone. This would bring together the different mythologies of the two shows.
How about a crossover with Supernatural? The Winchesters and the Shadowhunters could join forces. They both hunt supernatural beings, but their methods are quite different. The Shadowhunters' use of runes and their more organized society could contrast with the Winchesters' more free - spirited and on - the - fly hunting style. It would be fascinating to see how they interact and learn from each other.
One idea could be exploring the backstories of minor characters in the Shadowhunter Chronicles. For example, you could write about how a particular Silent Brother came to be. Another idea is to create an alternate universe where the Shadowhunters have different powers or abilities. You could also write a fanfiction focusing on a romantic relationship that was only hinted at in the original series.
A possible plot is a story where a character from Harry Potter accidentally travels to the Shadowhunter world. Let's say Neville Longbottom. He could end up at the Institute and be mistaken for a mundane at first. But as he starts to show his magical abilities, the Shadowhunters realize he's from a different kind of magic. He could then share his knowledge of herbology with them, which could be useful in creating new potions or antidotes in the Shadowhunter world. In return, he could learn about their combat techniques and bring some of that knowledge back to Hogwarts.
Well, it depends on how it's executed. If it's just a simple idea thrown together without much thought, it might not be that great. But if the author really delves into the differences and similarities between the two universes, like how the magic systems work and the different cultures of wizards in Harry Potter and Shadowhunters, it could be a very interesting fanfic.
For a crossover with Doctor Who, the Doctor could be an interesting addition. He could bring his time - traveling abilities and vast knowledge to the Shadow World. And from the Shadowhunter side, Jace Wayland would be a good character to include. His charm and combat skills would make for some interesting dynamics with characters from other universes.
One interesting idea could be a crossover with "Moana". Elsa's ice powers and Moana's connection to the ocean could create a really cool dynamic. Maybe Elsa accidentally freezes part of Moana's ocean and they have to work together to fix it. Another could be with "Tangled". Rapunzel's long hair and her adventurous spirit combined with Elsa and Anna's journey in Frozen 2 would be exciting. Rapunzel could use her hair to help them climb mountains or cross chasms. A third idea is a crossover with "Beauty and the Beast". Belle's love for books and knowledge could help Elsa understand more about her powers and the history of magic in the Frozen world.
A Thundercats and Star Wars crossover fanfiction would be really cool. The Thundercats could be in the Star Wars universe, and their unique powers and weapons could be a great addition. Maybe the Thundercats could help the Jedi or the Rebels in their fight against the Sith or the Empire. For instance, Cheetara's speed could be useful in battles, and Tygra's illusions could be used to deceive the enemy.
There could also be a storyline where the academy is under threat from an outside force, like a group of demons that are specifically targeting the young Shadowhunters in training. The students then have to band together, using their unique skills and the knowledge they've gained at the academy to fend off the attack. This would show their growth and development as future protectors of the Shadowhunter world.
A Digimon and Sailor Moon crossover is an interesting concept. The Digimon could help the Sailor Scouts in their battles against the Dark Kingdom. The magical powers of the Sailor Scouts combined with the digital powers of the Digimon would create a really unique and exciting story. And a Digimon and Avatar: The Last Airbender crossover. The Digimon could be part of the different nations, and they could use their abilities to help Aang and his friends in their quest to restore balance.
One idea could be an Atreus crossover with the world of Harry Potter. Atreus could be a new student at Hogwarts, bringing his own unique skills and knowledge from his Norse mythology background. He might struggle to adapt to the magic of the wizarding world while also showing off his own combat and survival abilities.
Another option is a crossover with a post - apocalyptic world. The garou's survival instincts and combat abilities would be well - suited for this harsh environment. It could either be a lone wolf trying to survive or join a group of survivors, bringing its own set of skills and challenges to the group.