Andromeda was the daughter of Cepheus and Cassiopeia, king and queen of Ethiopia. Cassiopeia boasted that her daughter was more beautiful than the Nereids, and in revenge Poseidon sent a flood and a sea monster to plague the land. When Cepheus consulted the oracle of Ammon he was told that the problem would end if he exposed his daughter as prey for the monster. His people forced him to comply with the oracle, and he chained Andromeda to a rock by the sea. She was rescued by Perseus who killed the monster and married Andromeda. One of their children, Perses, became the ancestor of the kings of Persia.