Percy might face the challenge of the time paradox. For instance, if he goes back in time and changes something, it could have unforeseen consequences on the present and future. He might erase important events or relationships that were crucial for his development and the overall story. And dealing with the moral implications of changing time is also a big challenge. He has to decide when it's right to interfere with time and when it's better to let things play out naturally.
One challenge could be the misuse of his power. If he accidentally goes too far back or forward in time, he might end up in a situation that is more dangerous than the one he was trying to avoid. For example, he could end up in a time when the monsters are even more powerful.
One challenge could be controlling the poison precisely. If he's in a fight and wants to use the poison against an enemy but not harm innocent bystanders, it would be difficult. For example, if he's in a crowded area, a wrong move could endanger those he doesn't want to hurt.
Percy's time - controlling ability might add a lot of twists to the plot. If he can control time, he could potentially stop time to outwit his enemies. This would make battles much easier for him and his friends. Also, he could use it to relive certain moments to gain more information. For instance, if there was a mystery about an event in the past, he could go back and observe it closely, which would then drive the plot forward as he uses the new knowledge to solve current problems.
The environment could also pose a challenge. If he's in a really hot place, using his ice - controlling ability might be much more difficult as the heat could quickly melt the ice he creates. Also, if he's in a place with very little water vapor in the air, it would be hard to form ice in the first place, which limits his power usage.
Percy would face several challenges as the god of time. For starters, there would be the issue of time paradoxes. If he meddles too much with time, he could create paradoxes that could have unforeseen and potentially disastrous consequences. Also, he would have to deal with the jealousy and fear of some of the other gods and demigods. They might see his new power as a threat and try to undermine him. Additionally, managing the balance between using his time powers for good and not becoming too controlling would be a constant struggle.
He may face challenges in the magical realm. The magic in the Percy Jackson universe might not interact well with his cyborg parts. For example, if he tries to use his powers while his cybernetic parts are active, there could be some unforeseen consequences. Also, he may be an outcast in both the human world (because he's a demigod) and the demigod world (because he's now a cyborg), which could lead to a lot of emotional and practical difficulties.
One challenge could be dealing with jealous teammates. Since Percy is so talented in the water, some might envy his skills. Another is the pressure to always win. Everyone expects the team to do great with Percy as captain. Also, he might face difficulties in getting the team to work together if there are different personalities.
Percy might find that his super speed doesn't always help in social situations. For example, when he's trying to have a conversation with a slow - talking character or when he needs to be patient in a diplomatic situation. His speed could make him seem impatient or hasty, which might cause misunderstandings. And in some cases, using his super speed too much could tire him out, leaving him vulnerable at crucial moments.
Well, he might face the challenge of leaving his mortal life behind. His relationships with his friends and family could be strained. He'd have to deal with new powers that are probably overwhelming at first. And he'd have to adapt to the politics and rules of the godly world which are likely very different from what he's used to.
One way could be that it's a gift from a minor god. Maybe a god associated with fire secretly blessed Percy, giving him this power.
In the fanfiction, Percy's water - controlling ability might be the key to solving a mystery. Say there's a strange drought in the land, and Percy uses his power to figure out what's causing it. He might discover that there's an evil force sucking up all the water, and then he has to use his ability to fight against this force. This would not only involve his power but also his courage and intelligence, making the plot more complex and interesting.