Loki and Zuko could be main characters in such a fanfic. Zuko has his own journey of redemption and Loki has his own complex past. They could bond over their struggles with identity and family. Zuko's firebending skills would also be an interesting contrast to Loki's magic. They could either become enemies or form an unexpected friendship as they navigate the challenges in a world that combines the elements of Asgard and the Avatar universe.
Aang could be a great crossover character. Since he is from the previous Avatar cycle, his different approach to bending and his more laid - back personality compared to Korra could create interesting interactions. He could offer her wisdom from his own experiences as an Avatar.
One option for the main character could be the child of Jake Sully and Neytiri. This character would inherit the unique skills and knowledge of their parents and face new challenges in the ever - evolving world of Pandora.
In a crossover with The Lord of the Rings, Aang could be one of the main characters. He has his own connection to nature and could form an interesting bond with the Na'vi. He could use his airbending skills to navigate Pandora's floating mountains and help the Na'vi in their battles.
Obviously Naruto would be one of the main characters as the title implies he's the emperor. Another could be Sasuke. He might be Naruto's right - hand man or sometimes a rival within the new empire. From the Avatar world, Aang could be a major character. He could either be an ally or someone who initially doubts Naruto's rule but later comes to respect him.
Obviously, Neytiri would be one of the main characters as she is the one who is pregnant. Jake would also be a central figure, as he is Neytiri's partner. Their unborn child could also be considered a main character in a sense, as the whole story revolves around the pregnancy.
One interesting concept could be the merging of Loki's mischievous and complex personality with the unique world - building of Avatar. For example, Loki might find himself in the midst of the elemental bending cultures and cause all sorts of chaos and intrigue. Maybe he'd try to manipulate the different tribes for his own gain, or perhaps he'd be intrigued by the spiritual connection to nature in Avatar and it would change his own views on power and control.
Obviously Naruto would be one of the main characters. And from 'The 100', Clarke would likely be a main character as well since she is a central figure in her own show.
Well, for a 'transformers bayverse crossover fanfic', you could have Ironhide as a main character. He's tough and a great fighter, which would be useful in the often - dangerous situations in a crossover. From the Bayverse, a young scientist or inventor could be a main character. They could bring a fresh perspective and new ideas to the table when it comes to interacting with the Transformers. Also, Starscream could be a main character. His ambition and treachery would add a lot of twists and turns to the story, constantly causing problems for both the Transformers and the Bayverse characters.
In addition to Monika and the Shelter protagonist, there could be some side characters from both worlds that play important roles. For example, some of Monika's clubmates in her original game might also get involved. And in the Shelter, the friends or family members of the main character could be part of the story. They could all contribute to the development of the plot in different ways.
In a crossover with the Inhumans, Medusa could be one of the main characters along with the Birds of Prey. Her long, prehensile hair and leadership skills would create an interesting dynamic. Also, in a crossover with the Guardians of the Galaxy, Gamora could be a main character. Her combat skills and no - nonsense attitude would mesh well with the Birds of Prey.