A Giant Scorpion is a huge monster scorpion.
In response to Orion's overhunting, the earth Protogenos Gaea stirred from her slumber and sent a giant scorpion to poison him. When Artemis found Orion's deceased body, she honored him in the stars, with the scorpion in particular becoming the constellation Scorpio.
Under the alias of Quintus, Daedalus bought the giant scorpions from the Triple G Ranch. He kept them in their boxes in the Sword Fighting Arena at Camp Half-Blood. He eventually let them out in the Camp Half-Blood Forest during Capture the Flag.