Well, they might embark on a journey to find a lost magical artifact. Since Emmett is physically powerful and Bella is quite intelligent, they could combine their skills. Emmett could handle any physical threats or obstacles, like fighting off wild animals, while Bella uses her wits to decipher clues leading to the artifact.
One possible adventure could be that they get transported to a different realm. In this new world, they have to find a way back home. Along the way, they meet all sorts of strange creatures. Emmett's boldness and Bella's ability to adapt quickly would help them survive. They would have to learn about the new realm's rules and use their combined resources to figure out a way to return to their own world.
In some fanfictions, they might be reimagined as siblings. However, in the original 'Twilight' series, they are not siblings. Fanfiction often takes creative liberties to explore different relationships between characters.
They could go on a quest to find a magical object that has the power to balance the magic in both their worlds. Since Percy is used to dealing with Greek mythology - related quests and Bella has her own experiences in the Twilight world, they could combine their skills. For example, Percy's ability to fight monsters and Bella's immunity to some vampire powers could come in handy.
They could have adventures across different dimensions. Since Loki has the ability to travel through different realms in the Marvel universe and Bella has her own experiences with the supernatural in 'Twilight', together they could explore places neither has been before. Maybe they visit a realm full of magical creatures that are a mix of vampires and Asgardians.
They could embark on a journey to find a lost Asgardian artifact. Thor's strength would be useful for any physical challenges they face, like fighting off monsters guarding the artifact. Loki's trickery could help them get past tricky traps and illusions. Hela, with her death - related powers, could deal with any undead or dark magic they encounter along the way.
One type of story could be about family secrets. Maybe there are secrets within the Cullen family that only they as siblings are privy to, and they have to work together to keep them. Another could be a story of adventure where their sibling bond helps them face challenges in the vampire world.
Maybe they go on a journey to find a lost artifact that has the power to control both vampires and demigods. Along the way, they face various challenges like werewolves who don't want them to succeed and demigod enemies who see Bella as a threat. Percy would use her strategic thinking from her demigod training, and Bella would rely on her instincts from living in the vampire world.
There could be. Fanfiction writers are known for their creativity and for pushing the boundaries of the original source material. While the idea of Bella and Emmett as siblings is not in line with the traditional Twilight narrative, in the realm of fanfiction, anything can happen. But given the rather unusual nature of this concept combined with the 'lemon' aspect, it may be a bit more niche and harder to find.
Their relationship can be shown as a very protective one. Emmett, being the stronger one, might always be ready to shield Bella from any harm. For instance, if there are other characters who pose a threat, Emmett would step in front of Bella without hesitation.
One adventure could be them traveling to different magical and non - magical places together. Hermione could take Bella to Hogwarts for a while, and Bella could introduce Hermione to the world of the Volturi. They would face many challenges along the way, like dealing with Hogwarts' strict rules when a non - magical person like Bella is there, and Hermione having to deal with the dangerous vampires in the Volturi's territory.
They could go on a journey to find out more about their family history. Maybe there are secrets about their parents that they need to uncover. Along the way, they would face various enemies and challenges. Naruto's combat skills and Tayuya's unique jutsu would be put to the test as they protect each other.