Perhaps he gets the power of astral projection. He could send his spirit out of his body to explore areas that are otherwise inaccessible or to spy on his enemies. This would be a very useful power especially when dealing with secretive foes or trying to find hidden places in the mythological world.
One possible new power for Percy Jackson in fanfiction might be the ability to communicate with all types of mythical creatures, not just those related to the sea. This would expand his network of allies and give him more knowledge about the mythical world.
Well, in fanfiction, Percy could have the power to control storms on a global scale. Imagine him summoning massive hurricanes to defeat his enemies or using gentle rain to heal the land. It would be a huge upgrade from his existing water - based powers.
In Percy Jackson new elemental powers fanfiction, the power of time could be a new addition. A character might be able to slow down or speed up time in a small area, affecting the elements within it. For instance, if they slow down time around a fire, it would seem to burn more slowly. Also, the power of space could be introduced. This could allow a character to manipulate the space between elements, like pulling water from a far - off source or compressing air to create a powerful blast.
New powers can drive the plot forward by creating new challenges. For example, if Percy gets a power he can't control at first, he has to learn to master it while also dealing with his normal foes. This adds an extra layer of conflict.
He could gain the power of super strength that far surpasses his demigod strength. This would allow him to lift extremely heavy objects or even mountains. Another power might be the ability to control the very essence of the ocean on a global scale, not just local waters like he could as a demigod.
In fanfiction, Percy Jackson's lightning powers often get enhanced or modified in interesting ways. Some authors might have him control lightning in more precise forms, like creating lightning cages to trap enemies. It adds a new level of coolness to his already amazing abilities.
Well, in Percy Jackson fanfiction regarding water powers, it often involves the characters pushing the limits of what's known in the original series. Some fanfictions might show a character using water powers to heal others, as water is often associated with life. There could also be a story where a character with water powers has to face an enemy who has a power that nullifies water, forcing them to find new ways to fight and use their abilities creatively.
There could be a fanfiction where a character with ice powers is actually an enemy in the Percy Jackson world. They are trying to freeze over all the water sources, which would be a huge threat to the demigods. Percy and his friends have to figure out how to stop this ice - powered foe. They might discover that the only way is to find a way to combine fire and water powers in a unique way, like using the heat from Hephaestus - forged weapons along with Percy's water control to melt the ice and defeat the enemy.
If he gets a new and powerful ability, his friends might feel a bit intimidated at first. For example, if he can control time, they may worry that he could change things without their consent. But over time, they would learn to trust him with this power and it could actually strengthen their bond as they work together to use it for good.