A really interesting plot for Castlevania fan fiction would be to set it in a modern - day world where the legacy of Castlevania still exists. There could be a young hacker who stumbles upon ancient texts about the vampire hunters and Dracula. As he delves deeper, he discovers that there are still vampires and dark forces lurking in the shadows of the modern world. He then teams up with a descendant of the Belmont family to fight this new threat, which would be a great blend of old and new, and bring a unique twist to the traditional Castlevania story.
One idea could be exploring the backstory of a minor character in the game. For example, a sidekick of the main protagonist who has their own motives and secrets that tie into the overall lore of the Castlevania Lords of Shadow universe.
One idea could be that Alucard finds himself in a different realm or time period in the crossover. He could team up with characters from the other universe to fight a common evil that threatens both their worlds. For example, facing a powerful demon that has the ability to corrupt both the Castlevania world and the world he's crossed into.
An interesting plot could involve a crossover with a superhero. Imagine if a superhero like Batman was somehow transported into the Castlevania Lords of Shadow world. He would have to rely on his wits, detective skills, and gadgets in a world full of supernatural threats. He could team up with the Castlevania hero to take on the powerful lords and vampires. His non - superhuman abilities would provide a different perspective compared to the magic - based combat in Castlevania, and his moral code could also influence the way the story unfolds in this dark and often morally ambiguous world.
One idea could be that the OC is a powerful witch who has been sent to stop Dracula from his dark plans. She initially tries to fight him but then discovers there's more to his actions than pure evil. Maybe he's trying to save his kind from extinction in a way that seems wrong but has good intentions at its core.
One idea could be that Naruto characters are transported to the Castlevania world. Naruto, with his high energy and determination, could take on the role of a fearless vampire hunter. He might use his shadow clones to outwit the undead hordes. Sasuke could be a lone wolf type character in this new world, his Sharingan helping him detect hidden traps and enemies. Sakura could use her medical skills to heal those affected by dark magic in the Castlevania realm.
One idea could be a story where the Mandalorian has to team up with an old enemy to fight a new, greater threat. Maybe a powerful Sith Lord emerges and they have to put aside their differences.
One idea could be exploring a different origin for Toothless. Maybe he was part of an ancient dragon tribe that was thought to be extinct. Another could be a story where Hiccup discovers a new dragon species that has unique abilities and forms an alliance with them. A third idea is a time - travel fan fiction where Hiccup goes back in time to prevent a great dragon war from ever starting.
A great plot for Warframe fan fiction could be a Tenno getting trapped in a parallel dimension where the rules of the Origin System are all messed up. They have to find a way back while dealing with strange versions of familiar enemies. Or perhaps a story about a Tenno who discovers a hidden Orokin vault that contains not only powerful weapons but also a secret that could change the balance of power in the Origin System. Also, a plot about a Tenno's struggle to control a newly acquired and extremely powerful Warframe that has a mind of its own could be really engaging.
Well, you could have a survivor fan fiction where a contestant has a hidden skill, like being able to communicate with animals on the island. This could give them an edge in finding food and avoiding danger. Or perhaps a story where there's a traitor within the group, someone who is secretly working with the show's producers to create more drama. Also, a plot where the survivors find a map that leads to a hidden part of the island with a bountiful supply of food and shelter.
One idea could be that the Ghostbusters discover a new type of ghost that can possess technology. So they have to find a way to stop it from taking over all the electronics in the city. It would be a race against time as the city starts to descend into chaos with machines going haywire.