Origin of Athena:
When Zeus's first wife, Metis, became pregnant, an oracle prophesied that the son of Metis would overthrow Zeus just as Zeus had overthrown his father. In fear, Zeus challenged his wife to a contest of magic. Whoever could turn into a smaller animal won. Metis turned herself into a fly, and Zeus swallowed her. Soon after, he had a terrible headache. It felt like someone was in his head stabbing at all the soft spots in his brain. He called for Hephaestus to help him. The god of the forge lay Zeus's head down on his anvil and broke the skull with a hammer. Out of Zeus's head sprung Athena, dressed for battle and armed with a spear.

Appearances:
The Iliad
The Odyssey
Arachne
Perseus