At first, he may be confused. He doesn't understand why the camp that has been like a home to him would turn on him. So he might start to search for answers, going on a journey to figure out what really happened and who is behind his exile.
He could be angry. Percy has always been loyal to the camp, and being exiled unjustly would make him furious. He might vow to prove his innocence and show the camp they made a big mistake.
Percy could also be sad and a bit lost. The camp has been his community, his friends are there. Being exiled means leaving all that behind. He might feel like he has nowhere to go at first, but then gradually find his own path and new allies outside the camp.
In some fanfictions, he might be exiled because of false accusations. Maybe someone frames him for a crime he didn't commit, like stealing a powerful artifact from the camp's vault. The camp leaders, believing the false evidence, have no choice but to exile him.
In some fanfictions, Percy is heartbroken. He has considered the camp his home for so long, and being banished makes him feel lost and betrayed. He might go into a period of self - doubt, wondering if he really is as bad as they say.
He might be really angry at first. He's given so much to the camp, and being kicked out like that without a proper explanation would make him furious. He could storm off, vowing to find out the truth and clear his name.
Percy could also be very sad. He has so many memories and relationships at the camp. He might go into a state of depression for a while, not knowing where to go or what to do next. But then, he would probably start to think about how to get back in or how to make things right. He might start looking for evidence to clear his name if he was wrongly accused. He could also look for new allies outside of the camp who could help him in his situation.
He may also try to figure out what went wrong. Percy is a smart demigod, and he would likely not just accept the betrayal without trying to understand the cause. So, he might start investigating, talking to other characters who might have some insight, like the other demigods or even some minor gods who are friendly to him.
He might be angry at first. After all, he has done so much for Olympus. He could feel betrayed by the very beings he has fought to protect.
Perhaps Percy would try to understand the primordial's reasons for the betrayal. He's a smart and empathetic character. He might think that there was some misunderstanding or that the primordial was forced into it. So, instead of immediately retaliating, he could try to communicate with the primordial to clear things up. If that doesn't work, then he would be more likely to take a defensive stance rather than an offensive one, at least until he fully understands the situation.
Well, initially Percy would be confused. He would try to understand why someone he trusted would turn on him. Depending on the severity of the betrayal, he might isolate himself for a while, thinking that he can't trust anyone. But as he is Percy, he would also start to look for a way to clear his name and prove his innocence. He would use his wits and his skills to figure out what really happened and expose the truth. He may also have some internal struggle about whether to forgive the betrayer if the situation allows for it.
Percy might be initially confused. He's not always the most attuned to flirting, so he could just stare at Drew blankly for a moment.
Percy may also try to find loopholes. Given his cleverness and his experience in dealing with the complex world of gods and prophecies, he would look for ways to work around the control of fate. He could use his relationships with other characters, like Annabeth's wisdom or Grover's loyalty, to help him figure out how to gain more control over his own destiny in the fanfiction.