The camp has magical borders which are enforced by the Golden Fleece, which was found and discovered by the satyr Grover, the Cyclops Tyson, and demigods Percy Jackson, Clarisse La Rue, and Annabeth Chase. Taken from Polyphemus's island it was placed on Thalia's pine tree, ensuring that no monsters could gain access to the camp. In earlier years it was a pine tree made from Thalia, a daughter of Zeus. After almost being killed by monsters, Zeus felt sorry for her and turned her into a pine tree, making it so she wouldn't die. Her tree became the official borders of Camp Half-Blood. The Fleece stayed on the tree, guarded by a dragon (Peleus), protecting the camp.