For a crossover with a fairy - tale world, characters like Cinderella could be included. The Sky Wizards could help her break free from her stepmother's control in a more magical and action - packed way. It would be a fresh take on the classic fairy - tale.
If it's a crossover with a superhero universe, characters like Superman could be interesting. The contrast between his superpowers and the magic of the Sky Wizards Academy would create great story potential. He could be both a helper and a source of conflict.
Maybe a crossover with a post - apocalyptic world. The Sky Wizards have to use their flying skills and magic to survive in a desolate land filled with new and dangerous threats. They could also team up with the local survivors who have their own unique abilities.
Levi Kazama is also a popular choice. Her determination and her skills as a sky wizard make her an exciting character to write about. You can explore her relationships with other characters, especially her rivals and friends in the academy.
I'm not entirely sure as I haven't read every detail of it, but usually in such a story, there would be a young and talented protagonist who is new to the academy. There might also be a strict but fair instructor.
In a crossover with Devil May Cry, Dante would be a great addition. His cocky and powerful attitude would contrast well with the more brute - force nature of the Splatterhouse protagonist. They could team up to fight some sort of demonic invasion that threatens both of their worlds.
Justin Russo is often a popular choice. His intelligence and powerful wizard skills make him a great character to interact with characters from other universes. He can hold his own in complex magical situations and often comes up with creative solutions.
John McClane from Die Hard would be a great addition. He has a similar tough - guy attitude and is good at handling high - pressure situations in urban environments. Another good character could be Ellen Ripley from Alien. Her experience with alien threats would contrast well with Rambo's combat skills. Also, Indiana Jones would be a perfect fit. His knowledge of archaeology and adventure - seeking nature combined with Rambo's combat expertise could lead to some exciting storylines.
Storm from the X - Men would be a great addition. She has control over the weather, which could create some really interesting scenarios when combined with Wolverine's combat skills. For example, she could create a lightning storm while Wolverine battles enemies in the rain, using the flashes of lightning to his advantage.
In a crossover with Hannah Montana, obviously Miley Stewart as Hannah Montana herself. She could be in Seattle for a secret concert and needs iCarly's help to promote it without revealing her identity. It would be fun to see Sam trying to keep Hannah's secret while also being her usual wild self around her.
In a crossover with the Lord of the Rings, Aragorn could be an interesting choice. He could bring his leadership skills and combat expertise to Los Santos. The GTA 5 characters might initially be skeptical of his noble ways, but they could learn from him. He could also help them fight against a new evil force that has emerged in the city, perhaps an ancient and powerful gang with dark magic - like abilities.
If it was a crossover with The Evil Within, Sebastian Castellanos would be a great character to include. His detective skills and his ability to handle the nightmarish creatures in his own game could be useful in the Outlast 2 world. He could team up with the Outlast 2 character to solve the mysteries behind the horror. Also, Pyramid Head from Silent Hill could be a terrifying addition. His presence alone would heighten the sense of dread in the Outlast 2 crossover story.