One idea could be to have the characters from RWBY end up in the world of Final Fantasy 15. For example, Ruby could meet Noctis and they could team up to fight some common enemy. Ruby's speed and scythe - wielding skills could be a great addition to Noctis' combat style.
The cultures of the two worlds could be explored in the fanfiction. The hierarchical society in RWBY with the Huntsmen and Huntresses could interact with the monarchy and different social classes in Final Fantasy 15. This could lead to political intrigue and new storylines as characters from both worlds try to understand and adapt to each other's cultures.
One common theme is crossover battles. Fans like to imagine how the characters from Final Fantasy 15 would fare against those from RWBY in combat. Another theme is friendship. Since both franchises have strong elements of friendship among the characters, fanfictions often explore new friendships that could form between characters from different universes. Also, power - up scenarios are popular, like a character from RWBY gaining a new ability inspired by Final Fantasy 15 magic or vice versa.
One way is through the combat systems. RWBY's fast - paced melee combat could be merged with FF15's more strategic combat. For example, Yang's brawler - style fighting could be enhanced with some of the weapon upgrades or magic from FF15. Another aspect is the character designs. The unique outfits and looks of RWBY characters could be combined with the more fantasy - based aesthetics of FF15. Maybe Blake could have a new look inspired by the clothing styles in FF15.
Well, it could be a mash - up full of action - packed battles. The Huntsmen and Huntresses from RWBY would bring their unique fighting styles to the table. In the FF15 world, they might encounter new types of Grimm or other menacing creatures. And the characters from FF15 could learn a thing or two from the RWBY gang about teamwork and using their individual strengths. For example, Weiss's ice magic could interact in interesting ways with the magic in FF15.
One interesting crossover could be the combination of RWBY's unique combat styles with Final Fantasy's magic systems. For example, Ruby's scythe - wielding skills might be enhanced with some of Final Fantasy's fire or ice magic spells. It would create really dynamic and visually stunning fight scenes.
First, you need to study the lore of both Final Fantasy XV and RWBY. Know the rules of magic, the types of Faunus in RWBY, and the world - building in Final Fantasy XV. Then, come up with an interesting concept. For example, a Faunus character from RWBY could be on a quest in the world of Final Fantasy XV. Next, create engaging characters. Make sure their personalities are distinct and their motives are clear.
In RWBY and Final Fantasy fanfiction, the world - building often combines elements from both. For RWBY, it's the four kingdoms with their distinct cultures and Dust - based technology. For Final Fantasy, there are diverse worlds like Gaia or Spira. Fanfic writers might merge the two by having RWBY characters visit a Final Fantasy world and be amazed by the different magic systems and cultures there. Or vice versa, Final Fantasy characters could come to Remnant and interact with the Grimm and Huntsmen.
One great 'Final Fantasy XV RWBY Faunus' fanfiction is 'The Faunus Among Kings'. It combines the unique elements of both universes really well. The story follows a Faunus character who somehow gets transported to the world of Final Fantasy XV. It has an interesting plot where the character has to adapt to the new world while also dealing with the discrimination they faced in their own RWBY world.
You can start by looking on fanfiction websites like Archive of Our Own (AO3). There are often tags related to both Final Fantasy 15 and RWBY, which can help you narrow down the search. Another option is FanFiction.net, although the tagging system there might not be as refined. Some Reddit communities dedicated to fanfiction or the respective franchises may also be a good source, where fans might share their favorite stories or even their own works.