Eurystheus

In Greek mythology, Eurystheus was king of Tiryns, one of three Mycenaean strongholds in the Argolid: Sthenelus was his father and the "horsewoman" Nicippe his mother, and he was a grandson of the hero Perseus, as was his opponent Heracles. He was married to Antimache, daughter of Amphidamas. In the contest of wills between Hera and Zeus over whom the hero would be, who would defeat the remaining creatures representing an old order and bring about the reign of the Twelve Olympians, Eurystheus ("wide strength") was Hera's candidate and Heracles—though his name implies that at one archaic stage of myth-making he had been "Hera's man"— was the candidate of Zeus. The arena for the actions that would bring about this deep change are the  Twelve Labors imposed on Heracles, by Eurystheus. The immediate necessity for the Labours of Heracles is as penance for Heracles' murder of his own family, in a fit of madness–that was sent by Hera, however; further human rather than mythic motivation is supplied by mythographers who note that their respective families had been rivals for the throne of  Mycenae. Details on the Twelve Labours are to be found at the article on Heracles, but Hera was connected with all of the opponents Heracles had to overcome.
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[Greek heroic] The king of Mycene, son of Sthenelus. By Hera's cunning, Heracles was for a long time subservient to Eurystheus. During that time he performed the so-called 'Twelve Labors'.