This is one of the famous labors of Heracles: these mares were man-eating horses who lived in far-away Thrace, in a land ruled by King Diomedes (not to be confused with the Homeric hero). Although there are various versions of the story, the different versions report that when Heracles finally subdued the horses he then fed King Diomedes to his own blood-thirsty beasts.
You can also find more myths and legends for the week of May 6-12 here. For more information and links to the actual javascript code, see the Myths & Legends Widget Reference Page.
