When Zeus, the King of gods abducted Europe, her brother Cadmus began searching for her everywhere. Soon he reached the city of Delphi, where he encountered the god Apollo, who told Cadmus to stop his quest and follow an cow. Wherever Cadmus would see the cow kneel, right there he was meant to establish a city.
Soon, they approached the area of Thebes, where the Greek hero Cadmus was confronted with a dragon and killed it. The dragon was a son of Ares, the god of war, and the Nymph Telphousa and was guarding the spring of Ares.
When Ares found out that someone killed his sacred dragon, he became furious and forced Cadmus to serve Ares for eight years as a slave in order to become purified. As a reconciliation, Ares gave Cadmus the hand of his daughter Harmonia. Their wedding was attended by all the gods, who endowed the couple with beautiful, precious gifts.
Following the advice of goddess Athena, Cadmus then sowed the dragon's teeth in the earth. Soon, fully armed warriors sprang up, the Spartoi, who were aggressive and very angry. Cadmus tried to defeat them by throwing stones at them, while the Spartoi thought that they were attacking each other and so they started fighting disorderly against each until finally they lost their lives.
Only five Spartoi survived: Echion, Oudaios, Chthonius, Hyperenor and Pelorus. Those five were the ones who founded the city of Thebes together with Cadmus and became the first citizens of Thebes. The citadel of ancient Thebes was named "Cadmeia" to honor the hero.