[citation needed] He was called Iasid Cepheus, pertaining to his Argive ancestry through King Iasus of Argus, father of Io.

Various sources describe his kingdom to be "Aethiopia" or later, the city of Joppa (Jaffa) in Phoenicia, which was named after the elder Cepheus's wife, Iope, daughter of Aeolus.

Cepheus and Cassiopeia seek guidance from the oracle of Ammon (identified with Zeus) at the oasis of Siwa in the Libyan desert; she declares the calamity will not end until Andromeda is offered to the monster as a human sacrifice.

Andromeda is saved when Perseus, flying home with his trophy head of Medusa, passes by the kingdom of Cepheus and notices a beautiful girl chained to a rock on the shore.

Since Cepheus has no heir of his own, the departing couple allows him to adopt their first-born child, Perses, who is destined to give his name to the Persians.