A more complex plot could be Percy getting caught in a time - loop created by an enemy who wants to stop him from fulfilling his destiny as the son of Hecate. In this loop, he has to keep reliving a certain day, but each time he learns something new about his powers or the enemy's plan, until he finally breaks free and defeats the enemy.
Another plot could involve Percy's relationship with other children of Hecate. Maybe there's a group of them that he has to lead in a battle against a common enemy. This would explore his leadership skills as well as his connection to his Hecate - related heritage. He might have to learn some ancient spells from them to defeat the foe.
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 having to master Hecate - related magic to defeat a new type of monster that is immune to physical attacks. Another could be Percy being chosen by Hecate to retrieve a powerful magical artifact from the underworld. And perhaps Percy must use Hecate's magic to save his friends who have been trapped in a magical maze created by an old enemy.
One idea could be Percy seeking help from Hecate to break a powerful curse that has been placed on Camp Half - Blood. Another could be Hecate tasking Percy with a quest to retrieve a magical artifact that she needs to maintain the balance of magic in the world. Maybe Percy has to enter the realm of Hecate and face various magical trials to gain a new power.
One interesting plot idea could be the OC using their Hecate - given powers to manipulate the Mist in unique ways. For example, creating illusions not just to deceive enemies but also to solve puzzles within the Percy Jackson universe. Maybe there's a quest where they have to use their magic to uncover hidden paths in an ancient labyrinth that's been magically altered by another deity.
One idea could be that the daughter of Hecate uses her magic to help Percy in a quest that involves navigating through a magical maze. She could create illusions to deceive the monsters inside.
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.