A possible plot could involve a magical object that has connections to both the Harry Potter world and the realm of Hades and Persephone. For example, a magical flower that can only grow in the underworld but has the power to heal the most deadly of curses in the wizarding world. Harry, along with Persephone and Hades, has to protect this flower from those who would use it for evil.
One idea could be exploring Persephone's adjustment to the Underworld. For example, she could start a garden in the gloomy realm using her powers over plants, which not only changes the look of the Underworld but also the attitude of its inhabitants. Another plot could be Hades trying to court Persephone in a more modern way, like taking her on a tour of different parts of the Underworld that are beautiful in their own dark way.
Well, you could have a plot where Persephone and Hades have an argument over her time split between the Underworld and the upper world. This could lead to her leaving for a while and Hades having to go through a series of trials to win her back. Another idea is that they discover a new part of the Underworld together that has been locked away for ages and it holds a great power. They must figure out what to do with this power without causing chaos in both their worlds.
You could write about how Hades and Persephone first met in a different way than the traditional myth. For instance, Persephone could be exploring the Underworld out of curiosity and Hades mistakes her for a lost soul at first. Then as they start to talk, they realize there's a special connection between them. This could lead to a whole new story of how their relationship developed from that unexpected encounter.
One plot idea could be Percy having to mediate a dispute between Hades and Persephone. Maybe something has gone wrong in the Underworld and their relationship is on the rocks because of it. Percy, being the hero he is, tries to find a solution that satisfies both of them.
One idea could be exploring their first meeting from a different perspective. Maybe Hades was initially more hesitant or Persephone was more curious than in the original. Another could be a story where they face a new threat to their relationship, like a jealous god trying to break them apart. A third idea is to write about their daily life in the Underworld, showing how they interact with the various creatures there.
One idea could be that Persephone, instead of being kidnapped by Hades in the traditional sense, she actually ventures into the Underworld out of her own curiosity. Hades is initially shocked but then becomes charmed by her boldness. Another plot could be a modern - day retelling where Hades is a powerful businessman in a dark and gloomy part of the city and Persephone is a young artist who stumbles upon his world. A third idea is that there is a curse on Hades that only Persephone's love can break, and they have to go through various trials in the Underworld and on Earth to be together.
A possible plot could involve Harry being drawn to the Underworld to learn more about his mother. There, he meets various figures from Greek mythology who either help or hinder him. His Hogwarts friends might not understand what he's going through, leading to some tense relationships as he tries to balance his two very different worlds.
One interesting interpretation could be that the kidnapping is not as malicious as it seems in the original myths. Maybe Hades is desperate to have Persephone in his realm because he truly loves her and sees no other way to be with her. He might be trying to show her a world she's never known before, a world that has its own beauty beneath the surface.
Well, in a Hades kidnapping Persephone fanfiction, you might consider making it a modern - day retelling. Hades could be a powerful business tycoon in a modern city, and Persephone a young, innocent girl. The 'kidnapping' could be more of a forced arrangement by Hades, but then as the story progresses, they start to understand each other. Or perhaps show how the other gods and goddesses react to the kidnapping. Do they try to rescue Persephone? How do their actions or inactions shape the relationship between Hades and Persephone?
Perhaps a plot where Hades and Persephone have to prove their love to a council of the most ancient gods. They are given a series of tasks, like Hades having to bring light to a part of the Underworld without using the sun, and Persephone having to make a barren part of the Underworld fertile again. Through these tasks, their love deepens and they also gain more respect from the other gods.