One common theme is the exploration of their different personalities. Remus is often seen as more kind - hearted and empathetic, while Lucius is more cold and calculating. Their relationship in fanfics can be about how they bridge this gap.
You can try searching on some popular fanfic websites like Archive of Our Own (AO3). There are a large number of fanfics in various fandoms on it, and you're likely to find some great remus x lucius fanfics there.
The fanfic 'Moonlight and the Boy Who Lived' is also worth checking out. It focuses on the emotional connection between Remus and Harry. There are scenes that are both heart - warming and intense. The author pays great attention to detail, especially in depicting how their relationship evolves over time, starting from a simple acquaintance to something much more profound.
One common theme is friendship - turned - love. Since they start as friends as part of the Marauders, a lot of fanfics explore how that friendship deepens into romantic love over time. Another theme is loyalty. They've been through a lot together, and the fics often show how they remain loyal to each other no matter what.
One common theme is friendship turned into love. Since they are friends in the original story, many fanfics explore how their relationship deepens into romantic love. For example, they might realize their feelings during their time at Hogwarts.
Friendship is a very common theme. Their strong bond as the Marauders is often explored, showing how they rely on each other, protect one another, and have a lot of fun together. Another theme is loyalty. They are extremely loyal to each other, and this is often a central part of the stories.
I'm not sure if there is such a specific fanfic. Fanfic creation is very diverse, but this seems like a rather unusual and perhaps not very common combination. There are many fanfic platforms out there, but this concept might be a bit out of the mainstream.
The theme of forbidden love also exists in some Lucius x Harry fanfic. Their relationship is not a typical or expected one in the context of the original Harry Potter series. So some fanfics explore the idea of them having feelings for each other that are not easily accepted by the wizarding society around them, adding a layer of drama and conflict to the story.
One idea could be a story where Fred and George play a prank that accidentally involves Harry, Remus, Lucius and Severus. Maybe they create a magical item that goes awry and causes chaos among all of them. For example, it could make them switch personalities temporarily, leading to some very interesting and comical situations.
You could start with a scene at Hogwarts, like in the Great Hall. Fred and George are causing a bit of a ruckus, Harry is trying to stay out of trouble, and Remus is just watching with amusement. Then, Lucius arrives with some sort of business at the school, and Severus is there to greet him. This sets up the different personalities and the potential for conflict or cooperation right away.