A cruel man named Minos has spent years competing with his brothers to rule Crete, a Greek isle (岛). He needs to get an advantage over them. One way of gaining advantage in the Greek myths is to get a god on your side. Minos chooses the god of the sea, Poseidon. To show that he has his support, Minos asks Poseidon to send him an animal to sacrifice, a snow-white bull (公牛).