Once upon a time, King Eurystheus of Mycenae and Tiryns, commanded a labor to Hercules, the son of Zeus and Alcmene, to bring back alive the mares of King Diomedes of Thrace.
Diomedes, the son of Ares and Cyrene, ruled the warlike Thracian people known as Bistones, and he fed his mares with human flesh. The mares were so savage that their feeding-troughs were made of brass. Having unkempt manes and shaggy right till their hoofs, they had a wild gruesome appearance. They were tied with iron chains for they had great strength, and they tore apart the bodies of the unfortunate men, given to them as food. Their stables were littered with the remains of the torn men, and their caretakers were even more beastly than the beastly mares.
Hercules, along with a group of volunteers, sailed to Thrace. They overpowered the barbarian caretakers and drove all the mares away to the sea. The Bistones, arming themselves with terrible weapons of warfare, came to the rescue of the mares. Hercules made his minion Abderos, the son of Hermes of Opous in Locris, as the guardian of the mares and left to fight the Bistones. However, the young Abderos failed to control the unruly mares, who dragged him after them and thus, killed him.
Meanwhile, Hercules fought a fierce battle and he killed Diomedes, which compelled the Bistones to flee. When Hercules returned, he found the mares devouring Abderos, and snatching the half-eaten corpse of Abderos, he threw at them the corpse of Diomedes. Upon consuming the flesh of their master Diomedes, who had taught them to eat human flesh, the untamed mares became tamed. Thereafter, Hercules gave a tearful burial to Abderos, beside whose grave, he erected a city called Abdera.
Hercules brought back the tamed mares to Eurystheus, who set them free. Later, the mares wandered to Mount Olympus, where they were killed by wild animals.
Excerpt from the book “Once Upon A Time-II: 150 Greek Mythology Stories” by Rajen Jani