Apollodorus Labor 1
The Typhon was one of the giants who rose up against the gods after they had successfully suppressed the Titans. Some of the giants had a hundred hands; others breathed fire. Eventually they were subdued and buried alive under Mt. Etna where their occasional struggles cause the earth to shake and their breath is the molten lava of a volcano. Such a creature was Typhon, the father of the Nemean lion.
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.