A Skaven Assassin could be interesting. In a crossover with a modern - day or more stealth - based world, the assassin's skills would add a lot of tension. They could be sent to eliminate key targets in the new setting.
You could also include a Skaven Packmaster. If the crossover is with a world full of wild beasts, the Packmaster's ability to control and manage his rat - like minions could create some unique scenarios. He could try to tame the native beasts or use his horde of rats to overrun areas.
Grey Seer Thanquol is a great choice. His devious nature and ambition can drive a lot of the plot in a crossover. He could be the mastermind behind the Skaven's actions in the new world they cross into.
Another plot could be a crossover where the Skaven meet a group of powerful mages from another universe. The Skaven, being cunning, would initially try to deceive the mages and use them for their own gain. But as the story progresses, they find out that the mages are not so easily fooled and a battle of wits and magic ensues.
The Dark Eldar Archon is an obvious choice. He is a powerful and cunning leader in the Dark Eldar society, full of ambition and a thirst for power. His complex motives and devious nature can drive a lot of the plot.
In a Dorohedoro crossover with 'One Punch Man', Saitama would be an interesting addition. His overpowered nature would contrast with the often - more - gritty and complex power levels in Dorohedoro. Another good character could be Guts from 'Berserk'. His dark and brooding personality would fit well in Dorohedoro's gloomy atmosphere. Also, Edward Elric from 'Fullmetal Alchemist' could bring his knowledge of alchemy and his quest for truth to the Dorohedoro world.
In vegito crossover fanfiction, characters like Jiren would be great. His strength and stoic nature would make for some intense interactions with Vegito. Also, Android 18 could be included. She has her own unique set of powers and a strong will. Her presence could add some interesting dynamics, especially if she has to team up with Vegito against a common enemy. And don't forget Frieza. His evil nature and thirst for power always make for an exciting addition to any Dragon Ball - related story.
Kenny McCormick (Mysterion) could cross paths with Batman. Batman's detective skills and high - tech gadgets would make for an interesting dynamic with Mysterion's more 'underground' superhero style. They could work together to solve a mystery that spans Gotham City and South Park.
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.
For a crossover with a post - apocalyptic world, characters like Mad Max could be involved. He might see the homunculi as either allies or threats in the harsh new world. In a crossover with a cyberpunk world, characters like Neo from 'The Matrix' could be interesting. The homunculi could be part of the complex digital and physical world that Neo navigates, and he could help them understand the true nature of their existence in this new, high - tech world.
In a springtrap crossover fanfiction, characters like the Purple Guy could be included. Since he has a connection to Springtrap, it would make for an interesting story. You could also include some original characters, like a brave adventurer who tries to stop Springtrap. And perhaps a mad scientist who created or is trying to control Springtrap.
The Powerpuff Girls would be great. Unikitty could join forces with them to fight crime in Townsville. Her magical powers combined with the girls' superpowers would make for an unbeatable team.
Well, if you're doing a crossover with "The Wizard of Oz", Dorothy would be a great addition. She and Coraline could compare their experiences of strange new worlds. The Scarecrow, Tin Man, and Cowardly Lion could also add some interesting dynamics, like the Scarecrow's new perspective on Coraline's world and how different it is from Oz.