Finally, start writing! Don't worry too much about making it perfect at first. Just get your ideas down on paper. You can always go back and edit later. Focus on developing your characters, especially how they change or react in this new crossover situation. And remember to have fun with it. Fanfiction is a creative outlet, so let your imagination run wild.
When starting to write, create a vivid description of the new world and how the Fire Keeper enters it. Is it through a magical portal or some other means? Build on the existing lore of the Fire Keeper while also respecting the rules and lore of the crossover world. Use detailed descriptions to make the readers feel like they are in this new and exciting crossover universe. Start with an engaging opening scene that grabs the reader's attention and makes them want to keep reading to find out what happens next.
First, decide which other universe or franchise you want to cross Fire Emblem Heroes with. Then, research about the lore, characters, and settings of both. After that, come up with a basic plot. For example, if you're crossing with Naruto, you could start with a portal opening between the two worlds and Fire Emblem Heroes being drawn into the ninja world. Next, introduce your main characters from Fire Emblem Heroes and show their reactions to the new world.
First, think about the characters. Decide if you want to use the existing ones from the Spirit Animals series or create your own. Then, come up with a basic plot. It could be something as simple as a journey to find a lost spirit animal or a battle against an evil force threatening the spirit animal world. Next, consider the setting. Will it be in the familiar forests and mountains from the original, or will you create a new and unique location? Once you have these elements, just start writing. Don't worry too much about making it perfect at first.
You should also focus on character development. If you're crossing with the Fullmetal Alchemist world, consider how Chrollo would interact with the Elric brothers. He might see their search for the Philosopher's Stone as something he can use for his own purposes. Start with a small scene that sets the tone, like Chrollo arriving in Amestris and observing the alchemic practices there, and then build the story from that initial encounter.
First, decide which universe you want to crossover with Tracer. Then, research that universe thoroughly. For example, if it's a Star Wars crossover, know the rules of the Force, the different species, and the technology. After that, create a plot that involves Tracer being thrust into this new universe. Maybe she's chasing a villain through a wormhole that leads to the Star Wars galaxy. Start with an engaging opening scene, like Tracer suddenly appearing in the middle of a lightsaber duel.
First, decide which universes or characters you want to crossover with Gogeta. Then, think about the plot. It could start with a disruption in the Dragon Ball universe that leads Gogeta to another world. For example, if it's a crossover with the One Piece universe, it could be a mysterious energy that pulls Gogeta to the Grand Line.
First, decide which universe you want to cross Ichigo over with. Then, research the rules and characteristics of that universe. For example, if it's a crossover with the Star Wars universe, learn about the Force and the different species. Next, think about how Ichigo would fit into that world. What would his role be? After that, start with an interesting hook in your story, like Ichigo suddenly appearing in a strange new place.
First, decide which universe Gowther will cross over into. Then, think about how Gowther's character traits and powers will interact with the new world. For example, if it's a crossover with 'Naruto', Gowther's power to manipulate memories might be a big deal in a world where knowledge and hidden pasts are important. Just start with a simple scene, like Gowther arriving in the new world.
Begin with a hook. If it's a Sinbad and a historical fiction crossover, like with the Vikings. Start with a battle scene where Sinbad's ship is attacked by Vikings. This will immediately draw the reader in. Then, develop the relationship between Sinbad and the Viking characters. Show how they overcome their cultural differences and start to work together towards a common goal.
First, choose the two or more universes you want to cross over. Then, research the characters, settings, and rules of those universes thoroughly. For example, if you're crossing over 'Harry Potter' and 'Star Wars', know the magic in Harry Potter and the Force in Star Wars.