Another plotline could involve the eldest god having a prophecy related to Percy. This prophecy could force Percy to make difficult choices between his loyalty to his friends and his newfound role in the eldest god's plans. For instance, he might have to sacrifice a chance to save a friend in order to fulfill a greater purpose for the world as dictated by the eldest god.
In the Percy Jackson universe, it could be Chaos. Chaos is often considered one of the most ancient and powerful entities. If Chaos were the eldest god in the fanfiction, it would bring a whole new level of power and mystery. Percy would be dealing with a being that is essentially the origin of everything, and its motives would be very difficult to understand.
In some fanfictions, Percy might be sent back in time to a period when the gods were more actively involved in battles. He then has to navigate the complex politics of the time, deal with the more primitive and violent versions of the gods, and use his modern - day knowledge and skills to change the outcome of some crucial battles. This could also lead to him changing the future in unexpected ways, creating a whole new set of challenges for him.
Some fanfictions might explore a plotline where Percy's new status as the God of the Unseen causes a rift between him and his friends. His friends may feel that he's becoming too different or powerful. He could then have to struggle to maintain his relationships while also dealing with the responsibilities of his new role. Additionally, there could be a plot where Percy discovers ancient prophecies related to the God of the Unseen and has to figure out how to fulfill them without sacrificing his own values.
A frequent theme is the resurrection or return of the eldest gods. In some fanfictions, the idea that these long - forgotten or sleeping gods awaken to find a world that has changed drastically is explored. This can lead to all kinds of conflicts and reconciliations. Also, the concept of the eldest gods' domains is a big part of it. For instance, if a fanfiction focuses on Gaea, the earth goddess, it might explore how she views the modern world's treatment of the earth. And the theme of redemption can also be found. Maybe an eldest god has made mistakes in the past and now tries to make amends in the context of the Percy Jackson universe.
Another plotline could involve Percy making a deal with the God of Death. In this scenario, he has to fulfill certain tasks in exchange for something he desperately needs, like saving a friend's life. This would put him in a series of dangerous and morally challenging situations as he tries to complete the tasks without sacrificing his own values.
Nyx, the goddess of the night, is quite popular in fanfictions. Her dark and mysterious nature makes her an appealing character. Writers can play with her powers, such as her control over the night, dreams, and all the things that lurk in the darkness. She can be portrayed as a powerful and independent figure, or she can have complex relationships with other gods or demigods. Erebus, the god of darkness, is also a favorite. His connection to Nyx and his role in the primordial cosmos offer a lot of material for fanfiction writers. He can be a source of great evil or a misunderstood figure trying to find his place in the world of the story.
One possible plotline could be Percy's struggle with his new godly powers and how it affects his relationships. For example, his friends might be in awe or a bit intimidated by his new status.
In many fanfictions, a common plotline involves Percy being framed for a crime he didn't commit. He then has to clear his name while also fighting off the real culprits, which are often powerful monsters or devious demigods. Another plotline could be that a new prophecy emerges that only Percy can fulfill, but it puts him in direct conflict with some of his closest friends. Also, there might be a plot where a group of demigods decide to break away from the traditional Camp Half - Blood and form their own community, and Percy has to decide whether to join them or not.
Some fanfictions might explore what would happen if Percy had a different parentage. Maybe he was the son of a different god or goddess, like Hecate. This would completely change his powers and the way he interacts with the magical world around him. He could learn new types of magic and have a whole new set of challenges and adventures.
Many fanfictions also have a plotline where Percy as the God of Tides has to deal with the consequences of his new power. He might accidentally cause a natural disaster due to his inexperience with his godly abilities. Then, he has to find a way to fix it while also facing the wrath of the other gods who are angry about the disruption he has caused.