One idea could be a crossover with 'Nightmare on Elm Street'. Freddy Krueger could invade the 'Friday the 13th' world and start terrorizing the campers. Jason Voorhees would then have to face this new threat. It could be an epic battle of two horror icons.
You could also do a crossover with 'The Blair Witch Project'. Imagine the Blair Witch luring victims to Camp Crystal Lake. Jason is already there, and the two forces of horror interact. Maybe the Blair Witch tries to control Jason, or they end up competing for victims. This would create a really spooky and unique fanfiction.
One idea could be a crossover with 'Nightmare on Elm Street'. Jason Voorhees could find himself in Freddy Krueger's dream world. Maybe the two iconic killers start to compete for victims, which would create a really tense and spooky situation.
First, decide which two or more universes you want to cross over. For example, if it's 'Friday the 13th' and 'Alien', think about how the two different types of horror can blend. Then, introduce the setting. If it's at Camp Crystal Lake, describe the spooky atmosphere. Next, bring in the characters. Start with a character from one of the universes, like Ripley from 'Alien' arriving at the lake. Then, build the conflict. Maybe there are strange alien - like creatures emerging from the lake, and Ripley has to team up with Jason (in a strange way) to face this new threat.
One possible plot could be that the vampires from Twilight somehow end up in the world of Friday the 13th. Maybe they get transported there by a strange magical event. The vampires' powers would be a new and terrifying element in the already spooky Friday the 13th setting. They could either be enemies of Jason or form some sort of uneasy alliance with him.
Well, a cool plot could be that there's a portal that opens up and transports the RWBY world into the Friday the 13th universe. The characters then have to figure out how to get back while dealing with the killers and other threats in that world. Weiss could use her glyphs in creative ways to combat the danger.
Jacob, in his werewolf form, would be more likely to directly confront Jason. He's used to fighting against threats, and his strength and speed as a werewolf would make him a formidable opponent. However, he might be a bit overconfident at first, not fully realizing the unique danger that Jason represents.
Ruby's speed might increase even more due to the sense of danger from the Friday the 13th elements. She could be constantly on high alert and her scythe attacks could be more erratic and fast - paced.
There's also 'Jason and the Newcomer'. In this fanfiction, a new character arrives at Camp Crystal Lake with a mysterious past. This character seems to have an uncanny ability to sense Jason's presence. The story delves into their strange connection and how it affects the events at the camp.
You could also write a 'Friday the 13th' fan fiction from the perspective of a new camper who is unaware of the legend. This camper could start noticing strange things and gradually piece together the horror that awaits them, adding an element of mystery and suspense to the story.
In a crossover with another horror franchise, like 'Scream', the killer from 'Scream' could be revealed as the mastermind behind Jason's actions. So instead of Jason just being a mindless killer, he's being manipulated by someone else for their own twisted reasons. This would completely change the dynamic of the fanfic.
Naruto's Rasengan would be a very effective weapon in the Friday the 13th universe. He could use it to blast away any threats, like the masked killers or other dangerous creatures. His ability to create shadow clones would also be useful for scouting the area, as the Friday the 13th settings are often full of hidden dangers. He could send clones in different directions to look for exits or other survivors.