A more complex plot could involve Percy being caught in a feud between two powerful groups. One side wants to use his connection to Prometheus for their own gain, while the other side wants to destroy him to prevent any potential threats. He has to figure out who he can trust and how to use his heritage to his advantage in this dangerous situation.
Perhaps Percy has to go on a quest to find an ancient artifact that was once in Prometheus' possession. Along the way, he meets other demigods who are either helping or hindering him, and he has to use his wits and the unique abilities he got from his father to succeed.
One idea could be Percy going on a quest to find a lost artifact that was once Thetis'. He could face various sea monsters along the way. Another plot could be Percy having to prove himself worthy in the eyes of Thetis' family. Maybe he has to pass a series of trials in an underwater realm.
Well, a plot could involve Percy getting caught in a magical feud between different factions related to Hecate. He might have to use his combat skills along with his newfound magical abilities to resolve the situation. Also, a story where Percy has to protect a sacred place related to Hecate from monsters would be interesting. He could learn about the secrets of Hecate's magic in the process.
One idea could be Percy discovering his unique heritage as the son of Hades and Persephone and struggling to fit in among the other demigods. He might have powers related to the Underworld that set him apart, like the ability to control certain types of plants that grow in the Underworld. Another plot could involve him having to deal with the politics between the gods because of his parentage. For example, Zeus might be suspicious of him due to his connection to Hades.
Well, a cool plot could be that Percy discovers there are dark forces in the underworld trying to overthrow Thanatos. And he has to team up with some unexpected allies, like some minor underworld deities who are also threatened by this uprising. He might have to use his skills as a demigod and his new - found connection to Thanatos to fight these forces. It could also involve Percy learning more about the secrets of Thanatos and how his own fate is intertwined with the god of death.
Well, a cool plot for a 'Percy Jackson Son of Khione Fanfic' might be that Percy is sent on a quest related to his new heritage. He has to find an ancient artifact that is tied to Khione's power. Along the way, he meets other demigods who also have unique powers related to cold or ice. They initially don't trust him because of his dual parentage but as they face challenges together, they learn to work as a team. He also has to deal with the internal struggle of being different from what everyone expected him to be.
Well, perhaps in the fanfic, Percy is wrongly accused of a crime by Zeus. He then has to go on the run, all the while trying to clear his name. Along the way, he teams up with some unlikely allies, like a group of nymphs who have their own reasons for helping him. As he's on the run, he uncovers a conspiracy within the Olympian council that could change the fate of the demigod world forever.
One idea could be Percy discovering his connection to Hera later in his adventures and having to deal with the reactions of his friends. Another could be him having unique powers inherited from Hera that set him apart from other demigods.
One idea could be Percy discovering new powers related to being the son of Hades. For example, he might be able to control the shadows in a unique way that no other demigod can. He could use this power to spy on enemies or to travel quickly through the underworld.
Well, perhaps a plot where Percy has to enter Kronos' old lair to find a way to break a curse that is affecting his friends. He could face many challenges and traps there. Also, a plot where Percy discovers that Kronos had a secret plan that he now has to carry out, but it conflicts with his loyalty to the Olympians.
Maybe the son of Hades in the fanfic has a special bond with a particular type of monster that is usually associated with death, like a Cerberus - like creature. Percy Jackson and his friends are initially scared of this bond but then realize it could be used to their advantage. For example, the son of Hades could use this bond to control the monster and have it help them in a battle against a common enemy. The fanfic could also explore how the son of Hades tries to fit into the world of Camp Half - Blood while being different from the other demigods.