Well, a cool plot might involve Percy being thrust into a situation where he has to mediate between Demeter and another god who has accidentally (or not) damaged one of her main domains. He could be championing Demeter's cause in a sort of divine court. Also, Percy could be involved in a story where he discovers an ancient prophecy related to Demeter that only he can fulfill as her champion, which leads him on a journey filled with mystery and danger.
The main antagonists could be the Titans who are still resentful of the gods and want to disrupt Demeter's power. Since Demeter is in charge of fertility and the harvest, the Titans might try to cause chaos in that area. Another option could be some dark nature spirits that have been corrupted and oppose Demeter's rule over nature.
In Percy Jackson fanfiction, the idea of Percy having a relationship with Demeter is quite an interesting concept. Demeter is the goddess of the harvest. A possible scenario could be that their love is based on Percy's respect for nature which Demeter represents. Maybe Percy helps Demeter in a quest related to protecting the harvest and in the process, they develop feelings for each other.
One interesting aspect in Percy Jackson and Demeter fanfiction could be the relationship between Demeter's powers over nature and Percy's adventures. For example, Demeter could use her powers to help Percy in a quest that involves a lot of natural elements like a forest that has been corrupted. She might be able to manipulate the plants to guide him or provide him with resources he needs.
Another idea in Percy Jackson and Demeter fanfiction is the idea of a friendship or a mentorship between them. Demeter could be like a mother figure to Percy, guiding him not only in matters related to nature but also in his personal growth. She could give him advice on how to deal with his complex family situation, using examples from the natural world she governs. This would add a very interesting emotional depth to the story.
Well, obviously Percy Jackson himself is often a main character. He's the hero of the original series, so in fanfiction related to Demeter, he usually plays a big role. Demeter is another main character, as the fanfiction is centered around her in some way. Sometimes her demigod children also make an appearance. For example, her daughter who might have some special powers related to plants or nature.
There might be a fanfiction where Demeter takes Percy under her wing to teach him about nature magic. In this story, Percy discovers new powers related to plants and the earth. He could use these powers to fight off enemies in a more unique way compared to his usual water - based powers. It would be a great character - development arc for Percy.
Often, it's portrayed as a somewhat unexpected pairing. Demeter, with her stern and earth - motherly nature, might initially be aloof to Percy. But as the story unfolds, she could see his good heart. For example, Percy might show kindness to the plants and animals under Demeter's care, and that could start to change her view of him.
Chiron is also likely to be a common character. He would be the one to help Percy adjust to his new identity as a son of Demeter. And there could be antagonists too. Maybe some monsters that are specifically targeting Demeter's children because of their connection to the earth and its resources. They could be trying to disrupt the balance that Demeter's children help maintain.
A powerful nature - hating Titan who wants to plunge the world into eternal winter could be a great antagonist. He would be directly opposed to Demeter's power over the seasons and crops.