Another option could be some power - hungry demigods. They might not like the idea of Percy, as the son of Themis, having the potential to bring real justice to the demigod world. They could try to undermine him at every turn, creating all sorts of obstacles for him in his quests.
One common theme is immortality. Since Marius is a vampire, his eternal life and how he copes with it is often explored. For example, he might face bouts of loneliness or have to constantly adapt to new time periods.
Another theme is the struggle with their own natures. Since they are complex characters, fanfics often deal with how they come to terms with who they are, whether it's their vampiric nature or their moral compasses. In many fanfics, they face internal conflicts related to these aspects. For example, in some stories, Armand may struggle with his past actions while Marius tries to guide him towards a more positive path. This exploration of their characters' growth and self - discovery is a very common and engaging theme in Armand Marius fanfic.
They are a popular couple in fanfiction because their relationship in the original story is so tragic and full of unrequited love. Fanfiction writers like to explore what could have been if things had been different. For example, if Marius had noticed Eponine's love sooner.
Cold tears and hot tears had different expressions. Cold tears usually had a sour, sad, sad, and other emotional tones. They could be tears shed in sadness, pain, or disappointment. Hot tears were more related to positive emotions such as excitement, happiness, and reverence. They might be tears that flowed when they were touched, happy, or with someone they liked. Therefore, cold tears and hot tears expressed different emotions.
One idea could be Percy discovers new powers related to being the son of Themis. For example, he might have the ability to see the true nature of laws and how they can be bent or broken in the mythological world. Another could be Percy having to mediate a major dispute between different camps using his connection to Themis, the goddess of justice.
I recommend you a modern romance and urban life novel,"Red Dust Twig Fence." It tells the story of how the small characters Chen Ziang and his sister struggled in the beautiful environment of the reform and opening up of the country. There was painful sadism, happy sweetness, reflection on responsibility, responsibility for morality, and appreciation for their love and hatred. I hope you like my recommendation, Mwah ~😗
Perhaps in the fanfiction, Cosette discovers she's pregnant at a time when there are political unrests in their city. Marius is involved in some sort of movement, and he has to balance his duties towards the cause and his family. Cosette, on the other hand, is worried about the safety of their unborn child. They have to rely on their friends and each other's love to get through this tough time, and the pregnancy becomes a symbol of hope in the midst of chaos.
Another theme could be the exploration of their individual growth within the relationship. For example, how Marius becomes more understanding of Cosette's past, and how Cosette becomes more confident in their relationship. It's about how they change and adapt to each other.