One possible plot is that Percy is contacted by a secret organization within the Allied forces. They know about his demigod status and need his help to deal with a series of mysterious disappearances of soldiers at sea. Percy discovers that there are sea monsters being used by the enemy to disrupt Allied supply lines, and he has to fight them while also trying to keep his identity a secret from most of the soldiers.
The plot could involve Percy being sent on a mission to stop the Axis powers from using ancient artifacts with mythical powers. He discovers that the Nazis are searching for a powerful relic that could turn the tide of the war, and he has to race against time to find it first.
In a Percy Jackson in World War II fanfiction, Percy might have to team up with some of the Allied soldiers. His sword fighting skills would be a great asset. He could also communicate with sea creatures to get information about enemy movements at sea. And perhaps he'd meet other demigods from different parts of the world who were also drawn into the war for various reasons.
One possible plot could be that the entire Greek pantheon is thrown into chaos. Percy might be seen as a huge threat, and other gods and goddesses would either try to hunt him down or form alliances with him out of fear or a desire for power. Demigods would be forced to take sides, leading to massive battles among them.
Perhaps the fanfiction could center around Percy discovering a hidden prophecy that is the key to ending the war between the gods. He then has to go on a dangerous quest to fulfill it. Along the way, he meets new allies and enemies, and has to use his wits and powers to overcome various obstacles. This could also lead to some character development for Percy as he faces difficult decisions and moral dilemmas.
One possible plot could be Percy and his friends dealing with the aftermath of the war in the mortal world. Maybe they have to hide their demigod identities even more carefully as the war has drawn some unwanted attention. They could also be working on rebuilding Camp Half - Blood and trying to make it safer for new demigods.
In the fanfiction, Percy might face new challenges related to his demigod status. Maybe he has to deal with the aftermath of the war, like rebuilding Camp Half - Blood or helping new demigods adjust.
One possible plot twist could be Percy finding out that a fellow soldier is actually a spy from the enemy side. This would create a lot of internal conflict as he has to decide what to do about it.
A great plot could be Percy being sent on a top - secret mission by the army. This mission could be related to some ancient artifact that has military applications but also ties to his demigod world. Along the way, he meets other demigods who are also in the military for various reasons. Together, they have to overcome not only military enemies but also mythical creatures that are after the same artifact.
Well, the plot might start with Percy being sent on a special mission by the gods. They need someone with his quick reflexes and sharp eyesight to be a sniper. Along the way, he has to deal with the moral implications of taking lives from a distance. He might also face challenges in terms of getting the right equipment and training. His friends could be initially skeptical of this new role for him, but as they see him succeed in various battles, they come to accept and rely on his sniper skills.
One possible plot could be Percy using his bike to travel across the country to find and protect other demigods. He could encounter various monsters along the way and use his biker skills, like sharp turns and high - speed maneuvers, to evade them.
One possible plot could be that a powerful enemy, let's say a dark sorcerer, has found a way to use the powers of the Greek gods against the supernatural beings in the Mikaelson universe. Percy Jackson is sent to investigate and ends up getting caught in the middle of the Mikaelson family drama. He has to use his skills as a demigod and his knowledge of Greek mythology to help the Mikaelsons defeat this new threat while also trying to keep his own identity and mission a secret from some of the more untrustworthy members of the family.