Cetus

Generic 'ketos' — the great sea-beast — sent by Poseidon to ravage the coast of Ethiopia after Queen Cassiopeia boasted she was lovelier than the Nereids. The oracle of Ammon prescribed that King Cepheus expose his daughter Andromeda to the monster; she was chained to a sea-cliff to be devoured. Perseus, returning from killing Medusa, saw her from the air, struck a bargain with Cepheus for her hand, and killed the beast — by sword in Apollodorus, by petrifaction with the Gorgon-head in the later iconographic tradition (Apollod. 2.4.3; Ovid *Met.* 4.689-739 for the Latin retelling).