Andromeda was a greek princess. Her mother Cassiopeia bragged that she was more beatiful than the nereids, nymph daughters of the sea god nereus. This bragging angered Poseidon and he sent a sea monster to ravage her kingdom. Zeus came down and told the king and queen that the sea monster would not stop unless they sacrifice Andromeda to it. As Andromeda was chained to a rock by the sea, about to be devoured, Perseus rescued her.