Final answer:
Cadmus, after visiting the Oracle of Delphi, followed a divine cow and founded Thebes where the cow rested. He killed a dragon and sowed its teeth, which grew into warriors that helped him build Thebes.
Step-by-step explanation:
After consulting the oracle of Delphi, Cadmus was instructed to follow a special cow and found a city where the cow would lay down; this city would become Thebes. The task was part of his search for his sister, Europa. Upon finding the site where the cow rested, Cadmus wanted to sacrifice the cow to the gods and sent his men to fetch water from a nearby spring. However, a dragon, which was sacred to Ares, killed his men at the spring. Cadmus then killed the dragon and, following the advice of Athena, sowed the dragon's teeth into the ground. This act resulted in the sprouting of fierce warriors known as Spartoi. After a confrontation, they killed each other until only five remained, who helped Cadmus build the city of Thebes. As a punishment for slaying Ares' dragon, Cadmus had to serve Ares for an eight-year indenture.