Another theme could be the contrast between the mortal and the immortal. In a 'lucifer romance novel', there is usually one human character involved. The differences in their natures, life spans, and perspectives create a lot of interesting plot points. The human may introduce Lucifer to the beauty and simplicity of the mortal world, while Lucifer shows the human the grandeur and mystery of the supernatural world.
One main theme is the idea of forbidden love. Since Lucifer is often associated with evil in traditional beliefs, a relationship with him is considered taboo.
The theme of identity is also prevalent. Given Lucifer's complex nature, light novels often delve into questions like who he really is. Is he the devil as defined by some religions, or is there more to his character? Novels may explore his identity in relation to other characters, such as angels or other demons.
Power is a major theme. Two Lucifers would bring a lot of power into one story, and it can be about who has more power or how they use their power together.
One main theme is the clash of different belief systems. Lucifer represents a very different view of good and evil compared to the Shadowhunters. Another theme is power dynamics. The powers that Lucifer has and the powers of the Shadowhunters are very different, and when they come together, there's a lot to explore about who has more power in different situations.
"Exalted Goddess Boss Please Have Respect" was a modern romance novel about urban supernatural powers. It told the story of the protagonist Qiu Ziwu meeting his big BOSS Lucifer by chance, as well as the adventure and love story of the two in the supernatural world. I recommend this novel to you. I hope you like it. Muah~
Power and its consequences are also a big theme. Naruto has his own set of powers in his universe, and when combined with Lucifer - who is often depicted as extremely powerful - it explores how these powers can be used, misused, or how they change the characters. This can lead to themes of corruption or self - discovery through power.
A common theme is power struggle. Lucifer, being a powerful figure, often gets into power - related conflicts with the RWBY characters who also possess various forms of power.
One common theme is redemption. When Lucifer is hurt, it can be a starting point for him to seek redemption for his past wrongdoings.
The theme of good vs. evil is common too. Chloe, representing the good, and Lucifer, with his devilish past, come together. Fanfics often play with this dynamic, like how they influence each other's views on morality and how they navigate the world with their different natures.
Power struggles are common. When Lucifer crosses over with other universes or characters, there's often a battle for dominance, like in crossovers with other powerful supernatural beings. Each character tries to assert their power and influence.
One common theme is loyalty. Fans often explore how Lucifer and Maze stay loyal to each other despite all the challenges they face. Another theme is self - discovery. Maze, in particular, is often on a journey to find out more about herself, and this is reflected in many fanfictions. And of course, friendship is a big theme. Their unique friendship, which is full of banter and deep understanding, is a central focus in a lot of fan - created stories.