Who could be the main characters in an 'x doom crossover fanfic'?

Definitely Geralt from The Witcher. His knowledge of monsters and magic could complement the Doom Slayer's brute force. They could work together to hunt down some powerful demons that are causing chaos in both their worlds.

Definitely Dipper and Mabel from 'Gravity Falls' would be main characters. And from 'The Replacements', Todd and Riley could be the main ones. They would be the ones driving the plot forward as they interact with the new and strange world or characters they encounter.

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.

Perhaps a crossover with a fantasy world. Doomguy enters a realm filled with magic, elves, and dragons. He might initially be seen as an outlander, but as he battles the demons that have also invaded this fantasy world, the inhabitants start to see him as a valuable ally. The clash between Doomguy's advanced weaponry and the magic of the fantasy world would be a fascinating aspect to write about.

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.

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.

For a more unexpected choice, you could have the Arbiter from Halo as one of the main characters. He has a complex backstory and his own code of honor. In a crossover, he could team up with a Hunter Guardian. The Hunter's brute strength combined with the Arbiter's strategic thinking would make for an exciting story as they face challenges in both universes.

Ayano could also be a main character. Her connection to Kazuma and her own abilities within the 'kaze no stigma' universe could bring a different dynamic. In a crossover, she might be the one to discover the secrets of the new world they enter or be the one who has to make difficult decisions about how to interact with the new characters.