For 10 points, name this founder of Thebes.
One of this god's children became immortalized as "the white  goddess" Leucothea. Hyginus describes how he was turned into a  serpent in Illyria, a fate which also befell his wife as well. He is one of  two title figures in a novel by Roberto Calasso. This son of Telephassa  had his own wedding in a namesake structure, where all the gods were  in attendance. He was condemned for an "eternal year" to serve (*) Ares.  This man killed a serpent at the Castalian Spring and ploughed dragon's teeth  to create the spartoi.  This son of Agenor abandoned his search for Europa  when he was told to follow a cow and found a city where it became exhausted.  For 10 points, name this founder of Thebes.
One of this god's children became immortalized as "the white  goddess" Leucothea.
Cadmus