The White Bull
The story is based on the Greek mythological tale of Europa and the bull, where the white bull is the king of the Greek gods, Zeus, in disguise. Zeus, the sky and thunder god of the Olympic pantheon, often wore a disguise when romantically pursuing mortal women, so as to avoid the eye of his wife and sister, Hera.
Aeschylus
In the trilogy's conclusion, "Prometheus the Fire-Bringer", it appears that the Titan finally warns Zeus not to sleep with the sea nymph Thetis, for she is fated to give birth to a son greater than the father. Not wishing to be overthrown, Zeus marries Thetis off to the mortal Peleus; the product of that union is Achilles, Greek hero of the Trojan War. After reconciling with Prometheus, Zeus probably inaugurates a festival in his honor at Athens.