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.
Prometheus the Fire-Bringer
Despite the paucity of direct evidence, Prometheus' foreshadowing of future events in the trilogy's first play suggests that the final play concerned itself with Prometheus' knowledge of a secret that could potentially lead to Zeus's downfall, and how the revelation of this secret leads to reconciliation between the Titan and Olympian. The secret is this: Thetis the Nereid, whom Zeus wants to take as a lover, is fated to bear a child greater than its father. Lying with her, then, would result in Zeus's being overthrown just as he had overthrown his own father, Cronus. During the course of the drama, Prometheus decides to warn Zeus about Thetis. Rather than lie with her, Zeus marries her off to the mortal Peleus, King of Aegina. The product of this union will indeed be a son greater than the father, namely Achilles, Greek hero of the Trojan War. Consequently, Zeus reconciles with Prometheus.