After Zeus had taken away Europa, the daughter of Agenor, he sent his sons to search for her and forbade them to return without her. Unable to find her, Cadmus travelled to Greece and asked the Oracle of Delphi where he could found a new city and was told to follow the first cow he would meet. Cadmus followed the advice and the first cow he met led him to Boeotia. He sent his men to fetch water for a sacrifice from a nearby grove but they were all killed by a dragon sacred to Ares. Cadmus went to search for them and meeting the dragon, killed it with a javelin. He was advised by Athena to sow the dragon's teeth and from the ground grew a group of armed who began to fight amongst themselves until only five were left who submitted to the service of Cadmus. With their help he founded the city of Thebes.
Cadmus eventually married Harmonia, the daughter of Hephaestus and they had four daughters named Autonoe, Ino, Semele and Agave and one son named Polydorus. Following the deaths of his children Ino and Semele and his grandchildren Actaeon and Pentheus, Cadmus and Harmonia left Thebes for exile in Illyria. The Encheleans chose Cadmus as their leader in their war against the Illyrians and achieved victory. Cadmus then reigned over the Illyrians and had a son named Illyrius. One day, when he grieved that the misfortunes of his house were due the dragon he had killed and wished that he was a serpent himself, after which he immediately transformed into a serpent along with Harmonia They were eventually taken to the Elysian Fields by Zeus.
- Apollodorus. The Library.
- Ovid. Metamorphoses.