Painting on an Attic red-figure plate, dating to about 550 B.C., now in the Louvre Museum, Paris. It represents the goddess Athena fighting against the Giant Enceladus. The Giants, sons of the Earth goddess, made an assault to Olympus and engaged in a furious struggle against the gods. Athena had a determining role in the fighting, which ended with the winning of the gods and the restoration of the cosmic order. This episode expresses Athena’s function as defender of the state against all exterior enemies and patroness of the city of Athens. The goddess appears always with her armor and helmet as a warrior, and with her shield which has at its centre the Gorgon’s head, the monster who petrified with her glance, and who, according to some traditions, was killed by the goddess. This shield, which was originally an attribute of Zeus, was called Aegis (from aix, “goat”) and was deemed to be realized by Hephaestus with a goatskin, according to some versions the skin of the goat Amalthea, the nurse of the infant Zeus.

[Source: http://en.wikipedia.org/wiki/Enceladus_%28mythology%29]