Well, there could be a fanfiction where Rayla and Callum are sent on a diplomatic mission to a group of neutral creatures in Xadia. Along the journey, they encounter various cultural differences and misunderstandings. As they work together to overcome these obstacles, their bond becomes stronger. This could also include some sweet moments between them as they share their thoughts and dreams under the starry Xadian sky.
A fanfiction could explore what would happen if Callum had an accident and lost his magic temporarily. Rayla would have to step up and protect him more than usual, and in the process, they might discover new aspects of their feelings for each other. Also, perhaps a story where they get trapped in a magical realm and have to find their way out, with only their love and trust in each other to guide them.
One idea could be a story where Rayla and Callum go on a secret mission deep into Xadia to find a long - lost magical artifact. They face many challenges along the way, and their relationship deepens as they rely on each other's skills. Another could be a fanfiction set in the future, where they have to deal with a new threat to the peace between humans and elves while also trying to start a family.