One possibility is that Percy uses his time - controlling ability to prevent a great disaster in his world. Maybe he goes back in time to stop an evil force from being unleashed in the first place.
In a 'Percy Controls Time' fanfiction, he might use his power to explore different eras. He travels to the past to learn ancient magic or secrets that could help him in his present. He could also accidentally change the course of history and then has to find a way to fix it without completely disrupting the world as he knows it. He might meet historical figures and have adventures with them while trying to keep the timeline intact.
In this 'izuku controls time fanfiction', perhaps he discovers his time - controlling power accidentally. He then uses it to explore different timelines. He might meet alternate versions of himself and his friends. This exploration of different realities could lead to him finding a way to make his own timeline a better place, like bringing back fallen heroes or preventing the destruction of parts of the city.
It could be another character who also has some time - related powers but uses them for evil. This character might try to steal Percy's time - controlling ability or use their own powers to disrupt the timeline for their own gain.
One possible plot could be that Percy, using his powers over water, manages to control the waters of the Styx in a way that he can manipulate its boundaries. He might use this ability to keep out unwanted creatures or to create a safe passage for his friends. For example, when his comrades need to cross the Styx but are being threatened by the monsters that lurk in its waters, Percy steps in and uses his control to calm the Styx and guide them safely across.
In this fanfiction, Percy might use his powers and leadership skills to bring order to the camp. Maybe he reorganizes the training schedules, making them more efficient for the demigods to improve their skills.
Well, in this fanfiction, Percy controlling the Styx could lead to some really interesting plot developments. Since the Styx has such a significant role in Greek mythology, it could attract all kinds of mythical creatures and gods. Percy could find himself in the middle of a power struggle as different factions either try to use him or stop him. He might also use the Styx to travel to different realms or access hidden knowledge. And perhaps he would have to face the consequences of messing with such a powerful and sacred entity, like facing the wrath of Hades or other underworld deities.
It could be that Percy's control of the Argo 2 is a result of some new power he has gained. This new power might attract the attention of both friends and foes. His friends might be in awe and a bit worried about this new development, while his enemies might see it as a threat. So, there could be a lot of political intrigue and battles as different parties try to either support Percy or take his newfound power away from him. And all of this while he is trying to use the Argo 2 to reach their ultimate destination.
In a 'Naruto controls snow' fanfiction, it could be that Naruto is cursed by an enemy. As a result, his chakra is somehow linked to snow. At first, he struggles to control this new power, but with the help of his friends and some intense training, he masters the ability to control snow and turns it into a powerful weapon against his foes.
Maybe she'd take control to better protect the students. She might enforce stricter security measures around the castle and grounds. Hermione is known for her caution and strategic thinking, so she could organize the defense of Hogwarts in a more efficient way against potential threats, like Death Eaters or other dark forces.
In 'naruto controls the darkness' fanfiction, it could also be that Naruto is exposed to a dark energy source accidentally. This energy starts to influence his thoughts and actions in negative ways at first. But being Naruto, he doesn't give in. He uses his strong willpower and the positive relationships he has with his friends like Sasuke, Sakura, and others to find a way to control this new dark power. He might have to face some of his own demons from his past, like the loneliness he felt as a child or the times he failed to protect his friends, and use these experiences to better understand and control the darkness within him.
One idea could be that Naruto discovers a strange new chakra within the headcrabs. He then figures out how to manipulate this chakra to control their actions. He might train them to perform tasks like scouting or even to help in rebuilding damaged villages by using their physical strength.