Often, Poseidon is depicted as heartbroken. He may withdraw from his normal duties and just sit in his underwater palace, watching over Percy's lifeless body or the place where he died. He could also be shown as being very quiet and solemn, his usual boisterous nature gone, replaced by a deep sense of loss.
Poseidon might be extremely angry. He could immediately seek revenge on the abuser. After all, Percy is his son and he has the power to protect him.
In fanfictions, Poseidon often interacts with baby Percy in a very gentle and protective way. He might use his powers to create a safe environment for Percy, like a special underwater grotto where Percy can be hidden from danger. Sometimes, he sends sea creatures to watch over Percy, like dolphins or friendly sea nymphs.
One possible plot could be Poseidon's grief and his journey to seek revenge for Percy's death. He might use his power to disrupt the world that allowed such a thing to happen. Another could be Poseidon trying to bring Percy back to life, going against the rules of the gods and facing many challenges along the way. Or perhaps Poseidon watches as the world changes after Percy's death, seeing how the other demigods step up or fall apart without Percy's leadership.
He might be extremely angry and feel a deep sense of hurt. After all he has done for Poseidon and the gods, being betrayed would shatter his trust. He could go into a period of self - exile, distancing himself from the demigod world and trying to find his own path without the help of his father.
This concept shows Poseidon as a god who adheres to certain values. He believes in teaching Percy right from wrong, which reflects his own sense of morality. It also portrays him as a bit traditional. In the world of the gods, where power can be used in many ways, he chooses this rather old - fashioned way of discipline, which might suggest that he has some conservative views on parenting.
Percy could initially feel shock and disbelief. He might try to talk to Poseidon to find out why he was betrayed. If that doesn't work, he could become angry and lash out, perhaps even challenging Poseidon directly.
In certain fanfictions, Poseidon might hurt Percy's reputation. He could do something that makes the other demigods look at Percy in a different, negative light. This could be by making decisions that seem to favor Percy too much, causing jealousy among others, or by getting Percy involved in some political mess within the godly realm that Percy has no control over. This can lead to Percy being ostracized or having to deal with a lot of unnecessary drama and pain.
At first, Percy would likely be angry. He has faced so many challenges with the belief that his father was on his side. The betrayal would make him feel like all his efforts were in vain. He could lash out, perhaps even using his powers in a more reckless way. But as time goes on, he might start to question if there's a deeper reason behind Poseidon's actions and try to find out the truth, especially if he still has friends who believe in him and encourage him to look deeper.
In some fanfiction, Poseidon's worry is shown through his direct actions. For example, he might send his messengers or minor sea deities to keep an eye on Percy. This shows that he is constantly concerned about Percy's well - being.
It can also make Percy more empathetic. Since he has such a powerful and protective father, he realizes the importance of protecting others too. He may be more likely to step in and help those in need, just as Poseidon does for him. This protection also gives Percy a sense of security that allows him to explore his own identity and powers more freely. He doesn't have to constantly worry about being alone or unprotected, so he can focus on growing as a hero and as a person.