Behead the 9 headed Hydra.
"For his second labour Herakles was instructed to slay the Lernaian (Lernaean) Hydra. The beast was nurtured in the marshes of Lerna, from where she would go out onto the flatland to raid flocks and ruin the land. The Hydra was of enormous size, with eight mortal heads, and a ninth one in the middle that was immortal. With Iolaos (Iolaus) driving, Herakles rode a chariot to Lerna, and there, stopping the horses, he found the Hydra on a ridge beside the springs of Amymone where she nested. By throwing flaming spears at her he forced her to emerge, and as she did he was able to catch hold. But she hung on to him by wrapping herself round one of his feet, and he was unable to help matters by striking her with his club, for as soon as one head was pounded off two others would grow in its place. Then a giant crab came along to help the Hydra, and bit Herakles on the foot. For this he killed the crab, and called on his own behalf to Iolaos for help. Iolaos made some torches by setting fire to a portion of the adjoining woods, and, by using these to burn the buddings of the heads, he kept them from growing. When he had overcome this problem, Herakles lopped off the immortal head, which he buried and covered with a heavy boulder at the side of the road that runs through Lerna to Elaios (Elaeus). He cut up the Hydra's body and dipped his arrows in its venom."