For the tenth of his twelve labors, Heracles had to bring the Cattle of Geryon back to Eurystheus. The Cattle of Geryon were a herd of powerful red cattle, owned by the Titan Geryon. This massive and dangerous Titan had three torsos to which three heads, six arms, and two legs were attached. His cattle were guarded by a two-headed dog names Orthandoleerus and a man named Eurythion. Getting the cattle would be a more difficult task than it seemed.
Heracles traveled to the land of Erytheia to complete his task. Upon arrival, he was confronted by Orthandoleerus. Heracles clubbed the beast and killed it with haste. When Eurythion came to aid the dog, Heracles clubbed him and killed him as well.
This angered Geryon, who chased Heracles carrying three shields and three spears. Heracles was corenered at the Anthemus River, but was able to shoot an arrow that had been dipped in the Hydra’s blood. He shot this arrow so powerfully that it stabbed all three of the Titan’s torsos. With that, Heracles began herding the cattle back to Eurystheus.
On the journey back, Heracles encoutnered a bit of trouble delivered by Cacus, a ferocious fire-breathing beast who ate human flesh (and was the son of Hephaestus). While Heracles was resting, Cacus stole part of the herd, having them leave no trail by walking backwards. Heracles found the cattle when he passed a cave, and the remainder of the herd began calling to the stolen animals. Heracles swiftly killed Cacus, and according to ancient Roman tradition, placed an altar at that location, which would become the Roman cattle market (Forum Boarium).
Hera, of course, had to make things difficult for Heracles. She started by sending pests to bit the cattle, causing them to scatter. It took Heracles one year to get them back together. She then flooded a river so he could not cross with the herd (he got around this by laying stones on the riverbed to make it shallow). At last, he handed the herd over to Eurystheus, who scarificed it to Hera.