His slaying of a sacred serpent at the Castalian Spring led to the eight years' penance he did to Ares, and also to his turning into a serpent at the end of his life with his 
His slaying of a sacred serpent at the Castalian Spring led to the eight years' penance he did to Ares, and also to his turning into a serpent at the end of his life with his wife. The father of Ino and Agave, he set out on a quest with his brothers Cilicix and Phoenix, before which his father Agenor instructed him to find his sister Europa after her kidnapping by Zeus. This led to his wandering off and eventually following a cow to the place where he would build a city. For ten points, name this husband of Harmonia and father of Semele and Polydorus, the legendary founder of the city of Thebes.
His slaying of a sacred serpent at the Castalian Spring led to the eight years' penance he did to Ares, and also to his turning into a serpent at the end of his life with his wife.
{Cadmus }