Eurystheus was a son of Sthenelus and Nicippe (or maybe Menippe), and he was the bitterest enemy of Heracles, who was enslaved to him while he carried out his Twelve Labours. A man to be reckoned with, therefore, as his name tells us, for it means 'widely powerful', for the same words as Eurysthenes. Note the echo of 'power' in his father's name.