What happened in Montauk that led Percy go to the summer camp?

In "The Last Olympian," Percy Jackson learns that he needs to go to the summer camp, Camp Half-Blood, after he receives a warning about an impending threat from Kronos and his forces. The events in Montauk, where Percy and his friends encounter danger from monsters, serve as a catalyst for him to seek refuge and training at the camp. This experience highlights the urgency of their situation and the importance of gathering allies to face the looming battle.