A cool Soul of Cinder crossover fanfiction could involve a crossover with the 'Bleach' universe. The Soul of Cinder's spiritual essence could be explored in the context of the Soul Reapers and Hollows in 'Bleach'. It could be a battle of different spiritual powers, and the Soul of Cinder might have to adapt to the rules and powers of the 'Bleach' world.
One idea could be a crossover with the 'Lord of the Rings' universe. The Soul of Cinder could be a powerful entity that somehow ends up in Middle - earth. Maybe it's mistaken for a dark lord by some and has to prove its true nature. Another option is a crossover with 'Final Fantasy'. The Soul of Cinder's abilities could be translated into the magic and combat system of 'Final Fantasy', creating some really interesting battles.
In writing a plot for a Soul of Cinder crossover fanfiction, consider the world - building aspect. If crossing over with the 'Legend of Zelda' series, how will the Soul of Cinder fit into the land of Hyrule? Maybe it's a dark force that has been awakened and the hero, Link, has to team up with other characters to stop it. Create a journey for the characters, with obstacles and revelations along the way. The Soul of Cinder's presence should disrupt the normal order of the 'Legend of Zelda' world, leading to a story full of excitement and mystery.
Another option is a crossover with a different anime world, like Naruto. GT Goku could end up in the Hidden Leaf Village. The shinobi would be amazed by his power. Goku, being Goku, would be interested in learning their ninja techniques. They could team up against a common enemy that somehow has the ability to use both chakra and ki, creating a unique and exciting battle scenario.
One idea could be to focus on the characters' different abilities. Blade's vampire - hunting skills and the unique powers of the Underworld vampires could create some intense fight scenes. For example, Blade could team up with Selene from Underworld to take on a new, more powerful vampire threat that combines the worst aspects of both their worlds.
A more complex scenario could involve a group of witches who are at war in their own realm. They decide to bring some of the powerful Naruto characters into their world to fight on their behalf. Naruto and his friends would have to adapt to the strange magic - filled environment and the political intrigue of the witches' war.
One idea could be a crossover with the X - Men. Spider - Man could team up with Wolverine. Their different fighting styles would make for some amazing action scenes. Wolverine's brute strength and healing factor combined with Spider - Man's agility and web - slinging abilities would be a great combination.
Another way to do this crossover is to have a prophecy that links Percy and Thor. The prophecy could say that only by the combined might of the son of Poseidon and the God of Thunder can a great evil be stopped. This evil could be a new kind of monster that has the ability to absorb both Greek and Norse magic. Percy and Thor would have to overcome their differences quickly. They would travel to different realms, both Greek and Norse, to gather items or allies needed to defeat this monster. Along the way, they would face many challenges and grow to respect each other.
Another interesting crossover could be with a superhero universe, say the Marvel universe. Picture Scorpion facing off against Spider - Man. Scorpion's hellish powers and acrobatic fighting style would make for an intense battle against the web - slinger. He could be there because he's been summoned by some dark magic that is affecting both worlds.
One idea could be to have the wizards from Harry Potter visit Azeroth. They could learn about the different magic there, like shamanistic magic or the arcane magic used by mages in Warcraft. Maybe Harry could befriend a young orc shaman and together they discover new spells by combining their magical knowledge.
One idea could be a crossover with Crash Bandicoot. Spyro could find himself in Crash's world, facing the same villains Crash does. They could team up to defeat Dr. Neo Cortex who has some evil plan involving both their worlds. This would bring a lot of action and humor as the two very different characters interact.
One idea could be a crossover with Ezio Auditore. They could team up to face a new, powerful Templar threat that spans across different time periods. Imagine the two assassins sharing their unique skills and knowledge.