A really interesting plot twist could be that she is the only one who can stop a great evil that is related to the Underworld. But to do so, she has to go against everything she was taught by Hades. This would create a huge internal struggle for her. Also, she might find out that there are other demigods like her, raised by 'unusual' gods, and they form a secret group.
One possible plot twist could be that she discovers she has a different parentage than she thought. Maybe Hades isn't really her father, but someone else who had a reason to leave her with Hades. Another twist could be that she has to fight against Hades at some point, even though he raised her.
Perhaps a plot twist could be that her connection to Hades actually gives her the ability to rewrite the rules of the Underworld. This causes chaos among the gods as they fear what she might do. And she has to deal with the consequences of this new - found power while also trying to protect the mortal world from threats that are coming from both the Underworld and other places.
One possible plot twist could be that Percy has a different set of powers. Since Hades is the god of the underworld, Percy might have an affinity for shadow manipulation or communicating with the dead in a more in - depth way than in the original stories. For example, he could be able to summon undead warriors to fight for him.
Perhaps the monster is from a different pantheon and is raising Percy to bridge the gap between two different mythologies. Percy then has to deal with the cultural shock and the politics of two very different mythological worlds while being raised by this strange being.
The story might focus on her struggle to fit in with the other demigods. Since she was raised by Hades, they might be suspicious or even afraid of her. But she could prove herself to be a hero in her own right. She could also have a unique relationship with the other children of the Big Three (Zeus and Poseidon).
One possible plot twist could be that Triton is not actually there to help Percy but is being controlled by an enemy to spy on him. So, Percy might think he has a new ally but in fact, he is being set up.
One possible plot twist could be that Percy, as the son of Hades and Hera, discovers a hidden power within him that can control both the underworld and the aspects of Hera's domain like marriage and family. This power could put him in the middle of a great conflict between the gods who are jealous of his unique abilities.
Perhaps a plot twist could involve Dionysus having a secret reason for raising Percy. It might turn out that Percy is part of some grand prophecy that only Dionysus knows about, and he's been grooming Percy for a specific task that will change the fate of the gods and demigods alike. This could lead to Percy having to make some really tough choices between his loyalty to Dionysus and his friends at Camp Half - Blood.
One possible plot twist could be that Artemis's blindfold is actually a self - imposed thing to gain a new power, and Percy discovers this secret halfway through the story. This would completely change their dynamic as Percy realizes he may not have been needed as much as he thought.
One possible plot twist could be that Percy's wolf - raised nature gives him unique abilities. For example, he might have enhanced senses like super - hearing or smell. This could change the way he approaches battles in the Percy Jackson universe. Instead of relying solely on his demigod powers, he could use his wolf - like instincts to outwit his enemies.
Well, a cool plot twist might be that the fem Percy Jackson raised by Hestia has a special connection to the underworld. Since Hestia is the goddess of the hearth, and the hearth is a symbol of life and warmth, her influence on Percy could make Percy a sort of bridge between the living world and the underworld. Maybe she can communicate with the dead in a unique way that no other demigod can. Also, it could be that Percy discovers she has an unknown parentage related to an underworld deity, which throws her whole identity into chaos. This would change her journey in the fanfic completely as she tries to figure out who she really is while still being raised by Hestia.
Well, it could involve Percy going on a quest specifically for Hades. Maybe he has to retrieve something from the Underworld that only he can do as the so - called 'Champion of Hades'.