Another possibility is that Percy is banished from Camp Half - Blood for some false accusation. He then becomes the lone warrior, wandering the world of mortals while still trying to protect them from the unseen threats of the mythological world. He might form new, unexpected alliances with mortals who have some latent powers or knowledge.
One idea could be that Percy, as the lone warrior, has to face a new threat alone. Maybe a powerful and ancient monster that has been awakened and no one else believes in its existence at first. He has to rely on his own skills and the limited resources he has.
Well, he could end up in a situation where all his friends are incapacitated. For example, they are put under a powerful spell. Percy then has to be the lone warrior to fight against a group of evil demigods who are trying to take over Camp Half - Blood. He'd have to use his water - related powers in new and creative ways.
Well, it could be about Percy going on a solo quest to find a powerful and lost artifact. Maybe he has to face some new and dangerous monsters all by himself, like a horde of fire - breathing dragons that guard the artifact in a hidden lair.
Perhaps an ancient and malevolent sorcerer who has been awakened from a long slumber. The sorcerer wants to use Percy's powers for his own dark purposes. He sets traps and sends magical creatures to stop Percy as he tries to figure out what the sorcerer is up to and how to defeat him. The sorcerer would be a very tricky antagonist as he can use all kinds of magic that Percy has never faced before.
Another plot could involve Percy being sent on a solo quest in a completely different realm, like the realm of dreams. He has to navigate through the strange landscapes and face the nightmares that come to life. He could discover a connection between the dream realm and the Greek gods that no one knew before, which could change the way the demigods view their powers.
One idea could be Percy having to face a new type of chaos monster that is immune to his usual powers. He would have to find a way to adapt and use his wits more than his strength. Maybe he teams up with an unexpected ally from the realm of chaos.
In a Percy Jackson Warrior of Olympus fanfiction, a great plot could involve Percy being sent into the future of the demigod world. He sees the consequences of the current actions of the gods and demigods. For example, he discovers that a war between the different pantheons has led to the destruction of many demigod camps. So, he has to go back in time and try to change the events that lead to this future. This would involve him having to convince not only his friends but also the gods to change their ways, which would be no easy feat as the gods are often stubborn. He might also meet some of his descendants in the future, and they could help him understand what exactly went wrong.
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 Percy discovers a hidden power within himself that makes him an even more powerful immortal warrior. Maybe he can control time briefly, allowing him to outmaneuver his enemies in battles. Another could be that he teams up with an ancient immortal warrior from a different mythology, like a Valkyrie from Norse mythology, and they have to combine their powers to defeat a new threat to the world of demigods. And perhaps there's a prophecy that only an immortal Percy can fulfill, which involves traveling to the Underworld and making a deal with Hades to gain an ultimate weapon.
One idea could be that Percy discovers a hidden power within himself that is related to the concept of a timeless warrior. Maybe he can time - travel in a unique way to different eras of Greek mythology and has to battle ancient evils that are starting to resurface in the modern world.
Survival is a big theme too. When Percy is all by himself, he has to rely on his own wits and skills to survive. This could mean finding food, shelter, and fighting off monsters without any help. In these fanfictions, we see Percy grow and become more self - reliant as he faces one survival challenge after another. He might start out a bit lost as a lone wolf, but as the story progresses, he becomes a stronger and more confident character through his survival experiences.