Perhaps Percy becomes withdrawn after Nico finds out, and Nico has to work hard to get Percy to open up again. This could lead to a deeper bond between them as Nico helps Percy heal. Another development could be that the discovery of Percy's abuse uncovers a larger conspiracy within the story's world, and they have to work together to stop it.
One possible plot development could be Nico seeking justice for Percy. He might start to investigate the abuse on his own and gather evidence against the abuser.
A possible plot development is that Nico tells some of their close friends about Percy's abuse. Their friends then form a support group for Percy. Meanwhile, Nico discovers that the abuser is still a threat and has to engage in a battle, either physical or magical, to keep Percy safe. This could also lead to Percy developing new powers or skills as he heals and learns to protect himself with Nico's help.
Perhaps there could be a plot where Annabeth discovers that the abuse has given Percy some hidden powers or a different perspective on his demigod abilities. So she encourages him to explore and master these new aspects of himself. Or, it could be that the news of Percy's abuse spreads among their friends, and they all come together to form a support system for him, which in turn strengthens their group as a whole.
One possible plot development could be Sally's intense anger and determination to protect Percy. She might seek justice against the abuser, which could lead to a showdown in the fanfic's world. Maybe she teams up with Percy's friends to expose the truth.
One plot development could be Lucius using this information to try and manipulate Harry. He might offer Harry a way out of his abusive situation in exchange for Harry's loyalty or some other form of service. For example, he could ask Harry to spy on Dumbledore for him.
After the discovery, a possible plot development could be that the champion takes Harry away to a secret location to keep him safe. From there, they might try to heal Harry's emotional wounds. As they do this, they could encounter various obstacles, like the abuser trying to find them or the wizarding authorities not believing their story. The champion might then have to prove Harry's situation, which could involve finding witnesses or evidence. Another development could be that the champion's actions draw the attention of a powerful and mysterious figure in the wizarding world, who either helps or hinders their efforts to protect Harry. This could lead to a whole new set of challenges and adventures in the fanfiction.
There could be a plot development where Remus and Sirius go on a journey to find a new place to start over, away from the abuser. Another development could be that Remus uses his intelligence to outwit the abuser legally. The fanfiction could also show how Remus helps Sirius regain his confidence and self - esteem. As Sirius heals, they might start to explore their relationship in a deeper way, whether it's a stronger friendship or something more romantic. There could also be a sub - plot where other characters get involved in different ways, some trying to help and some causing more trouble.
Nico might be initially shocked. He could feel a deep sense of anger towards whoever was responsible for Percy's abuse. Then he would probably become very protective of Percy, vowing to keep him safe from any further harm.
One possible plot development could be that Draco tries to expose the abuser. He might gather evidence secretly and present it to the right authorities at Hogwarts.
One possible plot development is that the gods gather to hold a trial for the abuser. They would bring in witnesses, and Percy would have to testify about what happened to him. This would be a very emotional and intense scene.
In some fanfictions, Paul could end up getting involved in the demigod world himself. Maybe he discovers he has some latent powers or a connection to the gods. This would completely change his perspective on life and his relationship with Percy. He could become a mentor figure for Percy in the mortal aspects of dealing with his demigod status.
The abusers might be ostracized by the community. Once Triton finds out and spreads the word, other sea - creatures or characters in the story might shun them. This could lead to them being isolated and having a hard time getting help or resources.