One idea could be Percy facing a moral dilemma where the will of the Primordials conflicts with his own sense of justice. Another could be him forming an unexpected alliance with a primordial being to save the world from a greater threat.
A plot could revolve around Percy being chosen as the Champion but then having to deal with the jealousy and suspicion of other demigods. He must prove that his role as the Champion of the Primordials is for the greater good and not a power - grab. He could also discover secrets about the Primordials that change his perception of them.
Perhaps Percy has to journey through the forgotten realms of the Primordials to retrieve a powerful artifact. Along the way, he meets strange creatures and has to overcome various challenges set by the Primordials themselves. This could involve tests of his strength, intelligence, and loyalty.
Maybe Percy has to fight against powerful primordial forces that threaten the world he knows.
There might be. A lot of fanfic writers are inspired by different concepts. However, it could be a bit niche, so you may need to do a thorough search on various fanfic websites. Check the tags related to 'Percy' and 'primordials' on those platforms.
The Titans who once fought against the gods could also be antagonists. They might view Percy's connection to the Primordials as a way to regain their power and oppose him at every turn. They could send their minions or use their own powers to try and stop Percy from fulfilling his role as the Champion.
One idea could be Percy being chosen as the Chaos Champion and having to face off against an ancient, long - forgotten evil that is emerging from the darkest corners of the Underworld. He'd have to use his new - found powers granted by Chaos in unique ways, like controlling the very essence of water in ways he never thought possible, such as turning it into solid light constructs for defense.
Well, a plot could involve Percy going on a quest specifically for Hestia. He might have to find a special artifact that is related to her. Along the way, he could meet new characters who are also loyal to Hestia. He would face challenges that test his loyalty to Hestia and his understanding of her values. For example, he might have to choose between saving the flame and saving his friends, and his decision would show his growth as a champion of Hestia.
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.
A great plot for this fanfiction could be Percy being summoned by the spirit of Ouranos himself. Ouranos could give Percy a task to unite all the different factions of demigods, including those who are usually at odds with each other, like the Romans and the Greeks. This would be a huge challenge as there are old grudges and differences in beliefs. Along the way, Percy would have to overcome his own doubts and the mistrust of others. He might also face some magical obstacles that are specifically designed to prevent the unification of the demigods, and he has to use his wits and powers as the Champion of Ouranos to break through them.
One idea could be Percy having to face a series of trials specifically designed by Hera to prove his worth as her champion. For example, he might have to navigate a maze filled with illusions based on Hera's past grudges.
Well, perhaps Percy in the fanfiction is faced with a moral dilemma related to his role as Champion of Styx. For example, he might be asked to make a sacrifice that goes against his principles but is necessary to save the world. Or he could be dealing with the jealousy and suspicion of his friends who don't fully understand his new powers and status. This could lead to some really interesting character development and story arcs.
Well, a plot idea could involve Percy being cursed by the fates to forget his own identity. He then has to go on a journey to rediscover who he is while still fulfilling his duties as the champion of the fates. Along the way, he might meet old friends who don't recognize him at first, and he has to prove himself to them. Or perhaps the fates send Percy on a mission to prevent a prophecy from coming true that would destroy the entire demigod world. This would involve him traveling to different mythological places and facing powerful enemies.