Another theme is the isolation Percy might feel. His new powers set him apart from his friends and he may have to deal with being alone or misunderstood. For example, his friends might be scared of his new abilities at first. It also often includes the theme of self - discovery as Percy figures out who he is with these new powers.
The theme of power corruption is also quite common. Percy has to fight against the temptation to use his dark powers in ways that could be considered wrong. The fanfic may show how he tries to resist the allure of absolute power and stay true to his values, which is not easy when you have such strong and potentially dangerous powers at your disposal.
One popular 'percy gets dark powers fanfic' is 'Dark Percy's Ascent'. It shows Percy's journey as he struggles with the new, dark powers within him. The story has great character development.
One common theme is self - discovery. When Anna gets powers, she often has to figure out what she can do with them and how they fit into her identity.
One common theme is the shattering of trust. When Percy gets betrayed, it's all about how that trust he had in someone is completely broken. This often leads to him feeling isolated and alone.
One common theme is power and its consequences. When Percy gets blessed, he often has to figure out how to control and use this new power without it getting the best of him.
One common theme is friendship. Since Percy has such strong bonds with his friends in the original series, many fanfics explore and expand on those relationships further.
One common theme is the corruption of power. In these fanfictions, the gods or demigods might abuse their powers, leading to a darker and more chaotic world. For example, a demigod could use their abilities for personal gain at the expense of others.
One common theme is the struggle between light and dark within Percy. His transformation into a darker version of himself often creates internal conflict. Another theme is the relationship between Percy and Artemis, which can be complex and filled with tension as they come from different backgrounds and have different natures.
One common theme is the struggle between good and evil. Percy, often associated with the good side, has to fight against the dark influence of the Dark Mark. For example, in many stories, he battles his own inner demons that the Mark seems to awaken.
One common theme could be the exploration of Percy's inner strength. Through the torture, the story might show how he endures and overcomes. Another theme could be the reaction of his friends. They might be desperate to save him, highlighting the bonds of friendship. Also, it could explore the motives of the torturers, whether it's for revenge or some other dark purpose.
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.