Heracles Labors: The Mares of Diomedes.
     The Thracian king Diomedes, son of Ares and the nymph Cyrene, fed his four mares on the flesh of men. Heracles (Hercules) was required for his eighth labor to bring these horses to Eurystheus. After overpowering the grooms, Heracles drove the mares to the sea, where he was overtaken by Diomedes. He killed the king, whose body was then devoured by his own horses. Having eaten their master’s flesh, the mares went tamely with Heracles. Eurystheus dedicated them to Hera and set them free, but they were eaten by wild animals on Mount Olympus.

Further Reference:
Galinsky, G. Karl. 1972. The Herakles Theme: The Adaptations of the Hero in Literature from Homer to the Twentieth Century. Totowa, N.J., Rowman & Littlefield.


Listings for Heracles' Labors are arranged under the following headings:
Heracles Labors, General List
The Nemean Lion
The Lernean Hydra
The Erymanthian Boar
The Ceryneian Hind
The Stymphalian Birds
The Stables of Augeas
Heracles and Antaeus
The Cretan Bull
The Mares of Diomedes
The Girdle of Hippolyta
The Cattle of Geryon
The Apples of the Hesperides
Cerberus

For Heracles entries generally:
Heracles