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.
One great 'braced httyd fanfic' could be 'The Bond Beyond Wings'. It delves deep into the relationship between Hiccup and Toothless in a new and exciting way. Another one might be 'Adventures in Berk's New Era' which shows how the characters adapt to new challenges while still maintaining their core relationships. There's also 'Dragon Riders United' which focuses on the unity among the dragon riders and their dragons.
Since 'sex httyd fanfic' is not an appropriate genre, I can't recommend any. Instead, try to find fanfics that are based on the original spirit of the HTTYD franchise, which is about courage, loyalty, and the co - existence between humans and dragons.
One popular RWBY HTTYD fanfic is 'Dragon Riders of Remnant'. It combines the unique elements of both universes really well. The characters from RWBY interact with dragons in a way that stays true to their original personalities.
First, you need to know both universes well. Study the characters, their personalities, and the settings of 'Brave' and 'How to Train Your Dragon'. For example, Merida is brave and headstrong, while Hiccup is intelligent and empathetic. You can use these traits to create interesting interactions.
One interesting HTTYD2 fanfiction is 'The Next Adventure'. It continues the story after the events of HTTYD2, exploring new lands and challenges for Hiccup and Toothless. It really captures the spirit of the movies.
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.
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 idea could be a story about a new dragon species that has unique abilities, like the power to control time. The main character discovers this dragon and they form a bond while trying to protect the dragon from those who would misuse its power.
One interesting 'httyd fanfic' story could be about a new dragon species discovered in a hidden valley on Berk. The main character, a young Viking, forms an unexpected bond with this dragon, which has unique abilities. This story could explore their adventures together as they face challenges from other Vikings who are skeptical of this new dragon.
There's a fanfic on FanFiction.net called 'When Dragons Meet Guardians'. It delves deep into how the characters from How to Train Your Dragon would interact with those from Rise of the Guardians. It's full of great character moments and has a well - paced story that keeps you hooked from start to finish. It also does a wonderful job of respecting the original lore of both franchises while creating something new.