In Greek mythology, the Cretan Bull was either the bull that carried away Europa or the bull Pasiphae fell in love with.

Capture by Herakles

Herakles was compelled to capture the bull as his seventh task. He sailed to Crete, whereupon the King of Crete, Minos, gave Herakles permission to take the bull away, as it had been wrecking havoc on Crete. Herakles used a lasso and rode it back to his cousin, Eurystheus. Eurystheus wanted to sacrifice the bull to Hera, who hated Herakles. She refused the sacrifice because it reflected glory on Herakles, and the bull was released to be captured by Theseus later.

Origin

When the sun has reached the constellation of Taurus, it has passed over an area that the ancients referred to as the sea - the region from Capricorn to the region containing Aries. It was referred to as the sea due to the high concentration of constellations identified as sea creatures within it, Aries being identified as a flying ram who flew over the sea. Crete is in a direct line from the natural harbour of Argo, a direction which the shape of Argo's harbour, and surrounding coastline, requires all ships initially take.

Apart from being a bull, Taurus contains a very bright and red star, meaning that many took it to be evil. Some forms of Greek mythology associated the constellation with the tame white bull, in some versions Zeus in disguise, that seduced Europa and took her to Crete (Minos), wheras others associate it with the white bull that fathered the Minotaur. The cretan bull which fathered the Minotaur was originally calm and sent from Poseidon, but the king (Minos) whom it was sent to fell out of favour with Poseidon, and so in some versions of the story, Poseidon made the bull angry.

The myth of Poseidon sending the bull (which seduced Minos' wife) may simply be an earlier version of the myth of Zeus seducing Europa, as in earlier Mycenean times, Poseidon had significantly more importance than Zeus. The change of gods was due to the replacement of the Mycenean culture and religion, with a later one favouring Zeus. Poseidon and Zeus, which have the same etymological origin (Poseidon deriving from Posei-Deion which means Lord God, and Zeus deriving from Deus which also means God), may be the result of the parallel evolution of the same original God in seperate cultures, one (Poseidon - who is also associated with horses) becoming associated more with the sea (due to change in the main source of trade), and thus eventually becoming noticably different.

Capture by Theseus

The bull was released and wandered to Marathon, becoming known as the Marathonian Bull, which Theseus was sent to try and catch. On the way to Marathon to capture the Bull, Theseus sought shelter from a storm in the shack owned by an ancient lady named Hecale. She swore to make a sacrifice to Zeus if Theseus was successful in capturing the bull. Theseus did capture the bull but when he returned to Hecale's hut, she was dead. Theseus built a deme in her honor.