One interesting plot twist could be that Percy, as the son of Vulcan, discovers a hidden power within him that's related to forging magical weapons. For example, he might be able to create a weapon that can only be wielded by those with a pure heart, and this weapon becomes crucial in a battle against an ancient evil. Another plot twist could be that his relationship with his father, Vulcan, is not as straightforward as he thought. Maybe Vulcan has been secretly guiding his enemies to test Percy's strength. Also, perhaps Percy finds out that he has a connection to an ancient prophecy that was long forgotten in the world of Vulcan's descendants, and this prophecy puts him in a position where he has to make a difficult choice between saving his friends or fulfilling a greater destiny.
One interesting plot twist could be Percy finding out he has some hidden connection to Ra's powers that no one expected. Maybe he discovers he can control the sun in a unique way, different from the normal demigod abilities. This could lead to a whole new set of challenges and adventures as he tries to understand and control this new power.
In some fanfictions, a really cool plot twist could be that Percy's Hela - given powers are slowly corrupting him. He starts to see the world in a different, darker way. His friends notice the change in him but don't know the cause at first. As he struggles with this corruption, he has to find a way to either embrace it and use it for good in a new way, or find a way to get rid of it. Also, imagine if Percy discovers that he has a half - brother or sister from Hela's side in the Norse world, and this new relative has a completely different view on life and power, which causes more drama and conflict for Percy.
One interesting plot twist could be that the Minotaur is actually a misunderstood creature under a curse. In some fanfictions, it might be revealed that he was once a heroic figure before being transformed. Another twist could be Percy having a secret power that he discovers while fighting the Minotaur that changes the whole dynamic of their encounter. For example, he might be able to communicate with the Minotaur's mind and find out its true motives.
A really cool plot twist might be that the reincarnated character realizes they are not just reincarnated into the Percy Jackson world randomly. They are part of a prophecy that was long forgotten. Their actions in this new life will either save or destroy the world of demigods. This would add a layer of high stakes and mystery to the fanfiction.
One interesting plot twist could be that the gods are actually players in this 'game' too. They manipulate events not just as deities but also as players with their own scores and goals. Another could be Percy finding out that his real power is not what he thought, like he has the ability to reset the 'game' world. And a third could be that some of the monsters are actually glitches in the game system, and Percy has to figure out how to deal with them in an unexpected way.
In some fanfictions, there could be a twist where the gods are not as all - powerful as they seem. Maybe they are being manipulated by a greater, unknown force. This would force Percy and his friends to re - evaluate their relationships with the gods and find new ways to deal with the threats to their world. It would also change Percy's destiny as he might have to take on a more independent role in saving the world without relying as much on the gods' help.
One possible plot twist could be that Percy discovers a hidden power within Tartarus that he can use to his advantage. Maybe it's a long - lost magic that only the darkest part of the Underworld can unlock.
Another plot twist might be that Tartarus itself has a weakness that Percy discovers by accident. For example, he might notice that certain sounds or vibrations can disrupt the structure of Tartarus. This would completely change the game as he could then use this knowledge to his advantage, perhaps causing mini - earthquakes to distract or even harm the monsters that are after him.
A great plot twist could be that Percy's transformation into a woman is not just a physical one but also gives her new powers or a different connection to the gods. Maybe she can now communicate with a goddess in a way that male Percy couldn't, and this new connection helps her on her quests in ways that are unexpected and exciting.
One interesting plot twist could be that Percy's control over the ocean is suddenly taken away by a dark magic spell. Then he has to find a way to get it back, perhaps by going on a quest to find a long - lost artifact or by making a deal with a mysterious sea - dwelling being. Another twist might be that the ocean starts to rebel against Percy's control. The sea creatures turn on him, and he has to figure out why and how to fix it.