The serpents were considered the protectors of the temples and the chthonic masters of the ancient earth goddess. In Greece the old oracles were devoted to the mother goddess. According to a Greek legend Apollo came to Delphi carrying Cretan priests. There he slew the daughter of Gaia, Python, who was the earth dragon represented as a serpent and possessed the oracle. At Dodona which is probably the oldest Greek oracle Zeus displaced the mother goddess and assimilated her with Aphrodite.At the oracle of Trophonius, Demeter-Europa was the nurse of chthonian Zeus-Trophonios who possessed the oracle. Wikipedia, Snake Goddess
We saw Apollo kill the python in Book I of the Metamorphoses. Many more references here.
On the figure pictured above, see this site.
For one possible historical view of Crete, see: The Chalice and the Blade
also: The Secret of Crete: