In Greek mythology, Andromeda was the daughter of Cepheus and Cassiopeia, king and queen of the Phoenician kingdom Ethiopia.
Cassiopeia bragged that she was more beautiful than Hera, Queen of the Gods and wife to Zeus. Poseidon, brother to Zeus, sent a sea monster, Cetus, to destroy the coast of Ethiopia and the kingdom of the vain Queen. The oracle of Ammon announced that no relief would be found until the king sacrificed his daughter Andromeda to the monster, so she was fastened to a rock by chains on the shore.
Perseus was Returning from having slain the Gorgon Medusa, found Andromeda, slew the monster and free her.