The twelve labors

In the second labor, Herakles was ordered to kill the Lernean Hydra, a monstrous serpent with nine heads living in the lake of Lernea.
With the help of his nephew, Iolaus, son of his brother Iphikles, Herakles found and fought the creature, in the spring of Amemone. Using a sharp sickle started cutting its heads, but in the place of a lost head, two new ones grew.
Herakles told his nephew Iolaus to light a torch, and burn the flesh immediately, after the cutting of the head. His idea worked and no more heads grew.
When finally cut the ninth head, which was in the middle and immortal, Herakles buried it deep in the earth and put on top an enormous stone and then in the bile of the monster, which was poisonous, he dipped his arrows.
King Eurystheus did not accept this feat to count, with the excuse that he was helped by his nephew Iolaus.