Apollodorus Labor 7
With the seventh labor, Hercules leaves the area of the Peloponnese to travel to the far corners of the earth and beyond. The first of the labors brings him only so far as Crete where he is to capture a bull whose identity is unclear, but whose indisputable nature is to cause trouble.
The bull may have been the one that Zeus used to abduct Europa, or it may have been one associated with Poseidon. King Minos of Crete had promised the beautiful, unusual white bull as a sacrifice to Poseidon, but when he reneged, the god made Minos' wife, Pasiphae, fall in love with it. With the help of Daedalus, the craftsman of labyrinth and melting-winged Icarus fame, Pasiphae had built a contraption that allowed the beautiful beast to impregnate her. Their offspring was the minotaur, the half-bull, half-man creature who yearly ate the Athenian tribute of fourteen young men and women.
An alternative story is that Poseidon revenged himself on Minos' sacrilege by making the white bull savage.
Whichever of these bulls was meant by the Cretan Bull, Hercules was sent by Eurystheus to capture it. He promptly did so -- no thanks to King Minos who refused to help, and brought it back to the King of Tiryns. But the king didn't really want the bull. After he released the creature, its troublesome nature -- held in check by the son of Zeus -- returned to the surface as it ravaged the countryside, traveling around Sparta, Arcadia, and into Attica.
