After Hercules had captured the Cretan Bull, Eurystheus sent him to get the man-eating mares of Diomedes, the king of a Thracian tribe called the Bistones, and bring them back to him in Mycenae.

Hercules sailed with a band of volunteers across the Aegean to Bistonia. There he and his companions overpowered the grooms who were tending the horses, and drove them to the sea. But by the time he got there, the Bistones had realized what had happened, and they sent a band of soldiers to recapture the animals. To free himself to fight, Hercules entrusted the mares to a youth named Abderos.

Horse and groom Tampa 86.29, Attic black figure neck amphora, ca. 490-480 B.C. Photograph by Maria Daniels, courtesy of the Tampa Museum of Art

Unfortunately, the mares got the better of young Abderos and dragged him around until he was killed.

Meanwhile Hercules fought the Bistones, killed Diomedes, and made the rest flee. In honor of the slain Abderos, Hercules founded the city of Abdera.

The hero took the mares back to Eurystheus, but Eurystheus set them free. The mares wandered around until eventually they came to Mount Olympos, the home of the gods, where they were eaten by wild beasts.