Poseidon had given a wonderfully beautiful bull to Minos with the expectation that Minos would sacrifice it to him. This bull indeed certified that Minos was the rightful king of Crete. Rather than sacrifice the bull to Poseidon, Minos kept it for himself. To punish him Poseidon had made Pasiphae, the wife of Minos, fall madly in love with the bull. With the aid of Daedalus Pasiphae let herself become impregnated by the bull. Daedalus made a hollow wooden cow for her to get inside, so she could mate with the bull. The resulting offspring which she bore was a monster called the Minotaur.