Originally from Phoenicia, brother of Europa. His search for his sister after her abduction by Zeus took him to Greece, where his companions were killed by a serpent guarding a fountain (Ovid, Metamorphoses, 3) he killed the serpent and was instructed to sow its teeth. From the ground where they fell armed men rose up proceded to kill each other until five were left, including Echion, father of Pentheus. The men who sprang up from the ground were known as Spartoi, meaning "sown men" (not to be confused with Spartans).
Kadmos then married Harmonia, their children were Semele, Ino, Agaue and Autonoe, mother of Actaeon. The couple were eventually transformed into serpents (Ovid, Metamorphoses 4). Euripides, Bacchae ends with a prophecy of this event.