Eurystheus sent Hercules to bring back the skin of the Nemean lion, but the skin of the Nemean lion was impervious to arrows or even the blows of his club, so Hercules had to wrestle with it on the ground in a cave. He soon overcame the beast by choking it.
When, upon his return, Hercules appeared at the gates of Tiryns, Nemean beast pelt on his arm, Eurystheus was alarmed. He ordered the hero henceforth to deposit his offerings and to keep himself beyond the city limits. Eurystheus also ordered a large bronze jar to hide himself in.
From then on, Eurystheus' orders would be relayed to Hercules through a herald, Copreus, son of Pelops the Elean.