In legend Cepheus (SEE-fee-us) was the Ethiopian King of Joppa; husband of Queen Cassiopeia and father of Andromeda. Legendary Ethiopia was not what we think of today, but a region near present-day Jordan and Egypt. Cepheus was a member of the crew of the Argo when Jason and the Argonauts quested for the Golden Fleece.

Cassiopeia had boasted that she and Andromeda were more beautiful than the Nereids (a group of sea nymphs), who complained of this insult to their protector, Poseidon. Poseidon sent a flood, followed by a sea-monster (Cetus) to devastate Philistia. When Cepheus consulted the Oracle at Ammon hoping to put an end the carnage, he was told that the only way to deliverance lay in sacrificing Andromeda to the monster. Her parents weren't enthralled with this idea but after all but they had an obligation to their people. So, she was chained naked to a rock except for her jewels and left to be devoured. The story continues from here with the introduction of Perseus and slaying of Cetus…Here is a brief version of the account:

Perseus (son of Danaë and Zeus – that Zeus was a true rascal) was flying by on his borrowed winged sandals on the way to Greece and just happened by Andromeda, chained naked to a rock, jewels glittering in the sun. He asked what she was doing and being somewhat shy, at first she didn’t answer, but eventually, told him the story and how she came to be bait for the sacrifice. Perseus, by this time had fallen deeply in love with her (a common mythological theme. Viewing her parents watching the proceedings nearby, he flew over to Cepheus and Cassiopeia indicating he would save her provided they gave their blessing to his marriage with Andromeda and allow her to return to Greece with him. They agreed and Perseus slew Cetus, turning the monster to stone with the Gorgon Medusa’s head, and he saved the Princess. Note: some accounts indicate he used the curved, adamantine sword given to him by Hermes (Mercury)for this slaying. Afterwards, Cepheus and Cassiopeia grudgingly welcomed him as their son-in-law at Andromeda’s insistence and the wedding was planned immediately. However, during the festivities, a suitor and rival named Agenor rudely interrupted the celebration with an armed party of supporters to claim Andromeda for himself. No doubt Cassiopeia summoned him as both she and Cepheus broke faith with their promise, stating it was made under the duress of the moment and Agenor’s claim preceded the arrival of Perseus.