Who was attacked at half-blood hill sea of monsters?

In "The Sea of Monsters," the second book of Rick Riordan's "Percy Jackson & The Olympians" series, Percy Jackson and his friends are attacked at Half-Blood Hill by a group of monsters known as the Cyclopes, specifically Polyphemus. This confrontation occurs as they try to protect the camp and its magical borders from being breached. The attack highlights the dangers the demigods face and sets the stage for their quest to retrieve the Golden Fleece.