A cool plot could be that there's a forgotten legend about a group of demigods who were banished long ago for a crime they didn't commit. Percy finds evidence of their existence and starts to believe that they might be the key to preventing a major catastrophe that is looming over the demigod world. He sets out to find these exiled demigods, but in doing so, he has to face the wrath of some of the more powerful gods who want to keep this part of history buried.
Maybe in the fanfiction, Percy stumbles upon a forgotten legend about a magical artifact that has the ability to rewrite the fates of demigods. The catch is that it's hidden in a realm that is slowly being consumed by chaos. Percy, along with his friends, must navigate this dangerous realm filled with strange creatures and illusions to find the artifact before it falls into the wrong hands. They'll also have to deal with the fact that the gods are not too keen on this artifact being found as it could disrupt their carefully crafted plans for the demigods.
One idea could be exploring the backstory of the forgotten warrior more in - depth. Maybe they were once a great hero in a forgotten era of the Percy Jackson universe and got lost in time somehow. Another could be that the forgotten warrior has a special power that is now needed to defeat a new, emerging threat. They could be a key to unlocking an ancient prophecy that no one has understood until now.
One idea could be that the forgotten one has a special power that is the key to saving the world from a new, unknown threat. Another could be that they are actually a long - lost relative of Percy's and their connection reveals hidden secrets about the demigod world. Maybe the forgotten one was sent away on purpose by an enemy long ago and now they're back for revenge.
One idea could be that the forgotten demigod discovers a hidden power within themselves that is related to an ancient and forgotten god. This power could set them on a journey to find out more about their heritage and also put them in a position to save the demigod world from a new threat.
One idea could be Percy having to face a new type of monster that is a combination of different mythological creatures. This would test his skills and knowledge in a whole new way.
Perhaps Percy has to go undercover in a mortal school as a completely normal student. But a new group of demigods is being targeted by an unknown force in that school, and he has to protect them without revealing his true identity. He'll have to deal with typical high school problems like bullies and exams while also fending off the mysterious threat.
A great plot could involve Percy going on a quest not for the typical reasons like saving the world or a camp, but to find a way to restore the memories of a friend who has lost them due to a powerful spell. Along the way, he discovers secrets about his own past that were hidden from him. He might also encounter new demigods with unique powers who either help or hinder his journey.
In 'percy jackson forgotten primordial fanfiction', there could be the idea of Percy having to deal with primordial forces that were previously unknown. This could lead to new alliances and challenges. Maybe he has to find a way to communicate with these forgotten entities, which would be a whole new aspect compared to his usual battles with known monsters and gods.
One plot idea could be Percy having to team up with Hera to rescue a group of demigods who have been captured by an ancient monster. Hera, despite her usual aloofness, realizes she needs Percy's unique skills.
A plot could be that Sally Jackson plants a lemon tree in her garden that turns out to be a gift from a minor goddess. The lemons from this tree have the power to give those who eat them the ability to see through illusions for a short time. Percy uses these lemons to his advantage when he is on a mission to retrieve a powerful artifact that is guarded by a monster that uses illusions to protect it.
Perhaps a fanfiction where Percy and Thalia are transported to an alternate dimension. In this new world, they have to figure out how to get back while also dealing with different versions of their friends and enemies. Thalia might have to face an alternate version of herself who has turned evil, and Percy could be the one to help her see the light again. It would be full of action, drama, and self - discovery.