One common theme is the power struggle. Nyx being an ancient and powerful goddess, often there are stories about her power in relation to Percy's abilities. Another theme is the mystery. Nyx is a rather mysterious figure in Greek mythology, and fanfictions like to explore that aspect further.
Well, often there's the theme of discovery. Percy discovers Nyx in a new light, perhaps seeing beyond her as a powerful entity to someone he could have feelings for. And Nyx might discover in Percy a sense of purity or courage that she admires. Also, the theme of transformation is common. Their relationship causes both of them to change, Percy might become more in tune with the primordial forces, and Nyx could become more understanding of the demigods. There's also the overarching theme of secrecy, as they may need to keep their relationship a secret from others in the world.
One major theme is the struggle between different generations of mythological beings. Percy is a more modern hero, while Nyx is from the very beginning of Greek mythology. Their relationship can be seen as a symbol of how the new and the old interact. Additionally, the theme of transformation is often present. Percy might be transformed by his encounter with Nyx, either in terms of his powers or his understanding of the world. And of course, the theme of the night and its secrets, since Nyx is the goddess of the night, is also quite common in such fanfictions.
One common theme is the struggle with identity. Since Percy is the son of Erebus and Nyx in these fanfictions, he often has to grapple with being different from the 'canon' Percy. Another theme is power. Given his new parentage, he might have different or enhanced powers, and the fanfictions often explore how he uses or controls them.
One common theme is the power dynamic. Since Nyx is a very powerful figure and Percy has his own set of powers, exploring how they interact in terms of power is often seen. For example, in some fanfictions, Percy has to learn to respect Nyx's greater power while still standing up for himself.
Well, a frequent theme is the exploration of the unknown. Nyx is from a different realm of existence compared to Percy. Fanfictions often deal with how Percy tries to understand Nyx's world and vice versa. Also, the theme of forbidden love is common. Since they are from different 'classes' in the mythological hierarchy, their love might be seen as something not allowed, which adds drama to the story.
One common theme is probably Percy's journey as the Champion. It could involve his training, the challenges he faces, and how he overcomes them. Another theme might be his relationship with Nyx, whether it's a master - apprentice kind of relationship or something more complex.
One common theme is the idea of an unlikely union. Percy, a demigod, and Nyx, a goddess, are from different strata of the mythological world, so their coming together is always an interesting exploration.
The theme of loyalty also pops up frequently. Percy has to decide where his loyalties lie - with his newfound heritage related to Nyx, with his old friends from Camp Half - Blood, or with the gods who now view him with suspicion. Fanfictions explore how he navigates these complex loyalty issues.
One common theme is the power dynamic. Given that Nyx is a very powerful figure in Greek mythology and Percy has his own set of powers, their relationship often explores who has more influence. For example, in some fanfictions, Percy has to learn to navigate Nyx's vast power.
Since 'lemon' fanfiction involves inappropriate content, we should focus on general themes in regular Percy and Nyx fanfiction. One common theme could be their different powers and how they interact with each other because of it. For example, Percy's water - based powers and Nyx's association with the night could create an interesting dynamic.