Once upon a time, Kadmos, the son of the Phoenician King Agenor, was ordered by his father to search for his sister Europa, who had been abducted by a bull, and not to return until he had found Europa. Kadmos roamed the earth but was unable to find his sister Europa or the bull.
Then, Kadmos consulted the Delphian oracle, who told him to abandon his search for Europa. The oracle advised Kadmos to follow a heifer that had never been yoked, and wherever the heifer rested, there Kadmos should build a city. Hardly had Kadmos left the oracle, when he saw a gentle-paced cow, without any scars of a yoke on her neck. He followed the cow, who finally rested at a place, where he decided to build the city of Thebes.
In gratitude for showing the place, Kadmos wished to sacrifice the cow to Athena. Hence, he sent his men to fetch water for the sacrifice. The men arrived at a beautiful lake, where a dragon, the son of god Ares, kept watch. As the men dipped their urns in the lake, the dragon appeared and killed them all. After some time, Kadmos wondering what detained his men, decided to go himself and see.
Kadmos approached the lake, and saw the dragon amidst the corpses of his men. Seeking to avenge the death of his men, the dauntless Kadmos fought a terrible battle with the dragon, and he finally slew the dragon. Athena appeared and instructed Kadmos to sow the teeth of the dragon in the ground. Kadmos obeyed and from that very ground arose armed warriors, who immediately began to kill each other. At the end, only five survived, as they dropped their weapons and stopped fighting.
To atone the slaying of the dragon, Kadmos diligently served Ares for an eternal year, which was equivalent to eight earthly years. Ares and Aphrodite were so pleased that they married their daughter Harmonia with Kadmos, in the presence of Zeus and other gods. Athena helped Kadmos build the city of Thebes, which Kadmos ruled.
Excerpt from the book “Once Upon A Time-II: 150 Greek Mythology Stories” by Rajen Jani