Obviously, Percy Jackson would be one of the main characters. He's the hero of the original series. And then, there's the forbidden warrior. We don't know much about this character yet, but they are likely to be a powerful and mysterious figure.
It's possible that some of Percy's friends from Camp Half - Blood could also be important characters. For example, Annabeth might be involved. She could be the one providing the knowledge and strategy as Percy and the forbidden warrior face different challenges. Grover might also show up, adding his own brand of support, perhaps with his nature - related abilities.
Another potential main character could be a villain. There might be someone or something that is opposed to the alliance between Percy and the forbidden warrior. This could be an old enemy of the demigods or a new threat that has emerged because of the presence of the forbidden warrior. So, in summary, the main characters would likely be Percy, the forbidden warrior, and potentially some of Percy's friends and an antagonist.
The plot might involve the forbidden warrior having some special powers or abilities that Percy has to figure out how to work with. It could be that the warrior was once banished or exiled for reasons that are gradually revealed. And Percy, being Percy, gets dragged into the whole situation, and they embark on a journey full of challenges and self - discovery. Along the way, they might encounter other mythical creatures and have to use their combined skills to overcome obstacles.
The gods and goddesses also play important roles in these fanfictions. Zeus might be a figure of authority that Percy has to deal with, especially if Percy's new - found ruthlessness starts to disrupt the balance among the demigods. Athena could also be involved, perhaps guiding Annabeth on how to handle Percy's transformation.
Percy himself is of course very popular. His heroic deeds and his journey from a somewhat naive demigod to a powerful warrior are always interesting to explore in fanfiction.
A powerful chaos deity could be the main antagonist. This deity might see Percy as a threat to their plans of spreading chaos throughout the world. They could constantly send their minions to attack Percy and try to corrupt his mind.
It might be a new, self - made god. This being has risen from the ashes of human greed and ambition. He sees Percy, the immortal warrior, as a threat to his plans of world domination. He uses his own brand of dark magic and his army of mind - controlled minions to try and defeat Percy. He also tries to turn the other gods against Percy by spreading lies and false prophecies about him.
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.
A powerful Titan who was once a timeless warrior but was banished to the depths of Tartarus could be a great antagonist. He has spent centuries plotting his revenge and now wants to use Percy to break free and destroy the Olympians once and for all.
It could be an old demigod from a long - forgotten camp. Maybe someone who was exiled or lost during a great war in the past. For example, a demigod who had the power to control the weather but was shunned because people feared their power.
Obviously, Atlas is a main character. He's often portrayed in different ways, sometimes as a more sympathetic figure trying to break free from his past, or as a more menacing antagonist still holding onto his old grudges. Percy Jackson also often shows up. His interactions with Atlas can range from confrontational to reluctantly allying with him.
Obviously, Percy Jackson himself is usually a main character. He is the one who gets involved in the devil - related situations. And then there could be new characters created specifically for the fanfiction, like a devil - like antagonist who is trying to corrupt Percy or the world around him.