Hendrick Goltzius, Cadmus Fighting the Dragon, circa 1600

Cadmus was the first hero in Greek mythology and founder of the city of Thebes. He seems to have been a real man known for bringing the Phoenician alphabet to the Greeks (it is the basis for the Greek alphabet), although his stories are based more on myth than fact.
Cadmus was just wandering around one day when he came upon the oracle at Delphi, who told him to follow a cow to wherever she finally laid down, and that he was to build a city there. He followed instructions and once there he decided to sacrifice the cow to Athena. He sent his friends Deioleon and Seriphus to get spring water for the sacrifice, but they were killed by the spring’s guardian water-dragon, so Cadmus goes over and slays the dragon. Athena instructed him to sow the dragon’s teeth like seeds, from which sprang an army of warriors. Cadmus threw a precious jewel between them, which they fought over, and only five remained standing. The remaining five helped him build the city of Thebes. ‘Sowing dragon’s seeds’ is a metaphor for fomenting arguments.