Percy might struggle with his new identity. He has been a demigod for so long, and suddenly becoming a primordial god means he has to re - evaluate his place in the world. He may miss his old life, his friends, and the simplicity of being a demigod. Adjusting to the new powers and responsibilities is not going to be easy.
As the god of fate, Percy has to deal with the chaos that can result from interfering with fate. Even a small change in one person's fate can have far - reaching consequences. He also has to be constantly vigilant against those who would try to manipulate him into changing fates for their own gain. The balance between justice and mercy in his decisions regarding fate is another big challenge. He can't be too lenient or too harsh, and finding that middle ground while dealing with the vastness of all the fates in the world is an extremely difficult task.
His character might become more aloof. As a primordial god, he would be far removed from the normal world of demigods. He'd likely have a different perspective on things like friendship and loyalty. For example, he might not be as quick to jump into a fight for his friends as he used to be, because his new status would bring a different set of responsibilities.
In fanfiction, if Percy Jackson becomes a primordial, it would be a huge shift in the narrative. He could be involved in the creation or destruction of new worlds. His personality might also change. He could become more detached, like many primordial beings are, as he now views the world from a much higher and more complex perspective. He might have to make decisions that affect the entire fabric of existence, and his actions would have consequences on a universal scale.
He could also face challenges related to the knowledge required to use his power effectively. In fanfiction, there might be ancient texts or prophecies that he needs to decipher in order to fully understand and utilize his new powers. But these texts could be written in a long - lost language or be guarded by powerful entities, making it difficult for him to access the necessary information.
If Percy Jackson were to become a hidden god in fanfiction, it would likely involve a lot of mystery and suspense. He'd have to navigate a world where he couldn't reveal his true nature easily and could potentially uncover some dark secrets along the way.
He might face the challenge of overtraining or undertraining. Since he doesn't have a coach or a training partner to tell him when he's doing too much or too little, he could end up either exhausting himself or not making enough progress. In fanfiction, he could also struggle with loneliness. Training by himself means no one to share his frustrations or small victories with. This loneliness could potentially affect his mental state and in turn, his performance. Additionally, without feedback from others, he may develop bad habits in his training that could be hard to correct later on.
The environment itself is a big obstacle. Tartarus is a place of extreme darkness and chaos. It can mess with Percy's mind, making it difficult for him to focus on his training. The terrain is also treacherous, with rivers of fire and bottomless pits.
In this type of fanfiction, it's a really interesting concept. One possible scenario could be that Percy's death is a heroic sacrifice. Maybe he gives his life to save the world from an even greater threat than before. And when he becomes a god, he might use his new powers to bring about a new era of peace among the gods and demigods. His transformation could also mean changes in his relationships. For example, his friends might now have to view him in a different light, as a divine being rather than just a fellow demigod.
He might gain new powers like controlling all aspects of water, not just the sea. He could also have the ability to create new sea creatures.
He might face mental challenges like PTSD. Tartarus is a horrible place, and the things he witnessed there could haunt him.