One idea could be that Demeter uses lemon in a special potion to help Percy on his quest. Maybe the lemon has some magical properties that only Demeter knows how to harness, and it gives Percy an edge against his enemies. For example, it could enhance his strength or give him the ability to see through certain magical illusions.
A third idea is that there's a prophecy involving Percy, Demeter, and a lemon. The lemon is a symbol of something greater, like a key to unlocking an ancient power. Demeter and Percy must work together to figure out what the prophecy means and how to use the lemon to save the world from a great evil. Along the way, they face challenges that test their friendship and their beliefs.
One idea could be Percy having to work with Demeter to save a magical grove that's being poisoned. Demeter could be initially distrustful of Percy, but as they face challenges together, she realizes his worth.
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.
One idea could be Percy exploring his new powers related to Demeter. Maybe he can control plant growth in unique ways, like making plants form protective barriers. Another could be his interactions with Demeter's other children. He might face some jealousy from them at first but then prove himself and form strong bonds.
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.
One interesting plot could be Percy having to learn about Demeter's powers and how to use them in a unique way. For example, he might discover a new form of plant - based magic that only a son of Demeter could access. This could lead to him using plants to fight monsters in a really creative way, like making thorny vines trap foes.
One interesting idea could be the crossover of Percy Jackson with other mythologies in a unique way in the fanfiction. For example, combining the Greek mythology elements from Percy Jackson with Norse mythology. This can create new and exciting adventures for the characters. Another aspect could be exploring different character relationships in a fresh light. Maybe seeing how Percy would interact with characters from another fictional universe in a situation that tests their loyalties and abilities.
One idea could be a crossover where Percy Jackson accidentally stumbles into the world of 'Rough Lemon'. Maybe he has to use his demigod powers to solve the unique problems there. For example, he could use his water - controlling abilities to deal with a drought that is plaguing the 'Rough Lemon' land.
One idea could be Percy using his water powers in a unique way against Medusa. For example, he could create a water shield that reflects Medusa's petrifying gaze back at her in a fanfiction. Another could be a scenario where Medusa, instead of being an enemy, teams up with Percy to face a greater threat.
A plot could be that Sally Jackson plants a lemon tree in her garden that turns out to be a gift from a minor goddess. The lemons from this tree have the power to give those who eat them the ability to see through illusions for a short time. Percy uses these lemons to his advantage when he is on a mission to retrieve a powerful artifact that is guarded by a monster that uses illusions to protect it.
One plot idea could be that Percy, while on a quest, stumbles upon a hidden grove dedicated to Hestia. There, he finds a lemon tree that has some sort of magical property. Maybe the lemons can heal the most severe wounds. And Hestia, in her role as the goddess of the hearth, has tasked Percy with protecting this tree from the forces of chaos that want to use its power for evil.