The plot could involve the Vikings of Berk discovering a magical link to the world of DunBroch. Hiccup, being the curious and adventurous type, decides to explore. He meets Merida and they quickly realize that there are threats in both their worlds that seem related. Maybe a dark force is trying to use the power of dragons and some ancient magic from DunBroch. Together, they must combine their skills, Hiccup's dragon - riding and knowledge of dragons, and Merida's archery and understanding of the magic in her land to defeat this common enemy.
One possible plot could be that a powerful dragon in httyd's world is being controlled by an evil sorcerer. This sorcerer has somehow also found a way to influence events in Merida's world. Merida notices strange things happening in her forest and decides to investigate. At the same time, Hiccup notices the dragon's unusual behavior. They cross paths and initially don't trust each other. But as they learn more about the sorcerer's plan, they understand that they need to work together. They embark on a journey that takes them through both worlds, facing various challenges along the way, from Merida's overbearing mother to Hiccup's doubting tribesmen.
A great plot for a crossover could start with a young dragon from Berk getting lost and ending up in Merida's land. The dragon is scared and starts causing some chaos. Merida tries to calm it down but realizes she needs help. She somehow sends a signal that is received by Hiccup. Hiccup and Toothless fly to her world. There, they discover that there is a group of people in Merida's land who are trying to capture the dragon for their own evil purposes. Merida and Hiccup have to protect the dragon and also find a way to send it back to Berk. Along the way, they learn about each other's cultures and develop a friendship that will last even after the adventure is over.
Once upon a time in the land of Berk, Hiccup was flying on Toothless when a strange magic portal opened. Out of it came Merida from the land of DunBroch. Hiccup was startled but curious. Merida was amazed by the dragons. They decided to team up. Hiccup showed Merida how to ride Toothless and in return, Merida taught Hiccup some of her archery skills. Together they went on an adventure to save both their lands from a common enemy that was using dark magic.
A great plot in this crossover fanfiction might be that an ancient threat from both universes resurfaces. In the HTTYD world, it could be an even more powerful and evil version of the Red Death. In the Avengers' universe, it could be a new group of super - villains. The Avengers and the HTTYD characters then have to combine their skills. The dragons could be used to transport the Avengers quickly across the HTTYD landscapes, and the Avengers could teach the Vikings about modern combat strategies.
The fanfiction might focus on how the relationships between the characters change when the two worlds of HTTYD and HTTYD2 collide. For example, Astrid might have to adapt to new ways of dragon riding she sees in HTTYD2, and this could cause some friction or growth in her relationship with Hiccup. It could also involve the dragons from the first movie learning new skills from the HTTYD2 dragons.
Perhaps the vikings of Berk accidentally open a portal to Spyro's realm while exploring a new area. Spyro is intrigued by the vikings and their relationship with dragons. Meanwhile, Hiccup tries to understand Spyro's abilities and how they can be used to improve Berk's defenses. They could team up to rescue some baby dragons that were captured by an evil force from both their worlds.
A powerful dragon - mage hybrid could be the main antagonist. This creature could have the ability to control both the dark magic from Spyro's world and the power of the more menacing dragons in HTTYD. It wants to rule both worlds and is using its magic to create chaos and turn the dragons against each other.
The plot could involve Hiccup joining the marines to seek new adventures and knowledge. Once there, he discovers that the marines have their own set of problems, such as dealing with internal politics and external threats. Hiccup, with his kind heart and determination, tries to make a difference. He might introduce some of the Berkian technology or ideas to the marines, like new ways of building defenses or navigation techniques.
There is a 'brave httyd fanfic' called 'Alliance of Heroes'. In this fanfic, the main characters from 'Brave' find themselves in Berk and team up with Hiccup and his friends. They face a common enemy and it's really interesting to see how their different skills and personalities blend together in the story.
Well, it could be like Merida joining the Avengers. Maybe she uses her archery skills to help them in a battle. For example, in a fight against some powerful alien invaders, Merida's precise shooting takes out key enemies, impressing the likes of Hawkeye and Black Widow. She could also teach them some wilderness survival skills that are useful during their off - base missions.
One popular idea is a httyd and How to Train Your Knight crossover. Imagine the dragons in a world filled with knights and castles. Another could be a crossover with a modern - day setting, like httyd characters in a big city dealing with new challenges. And there's also the idea of a crossover with a fantasy world like Middle - earth, where the dragons interact with different magical creatures.