Final answer:
Herakles needed to complete labors for his cousin Eurystheus as a punishment for his madness-induced murder of his family.
Step-by-step explanation:
According to various sources, including Apollodorus' Library, Herakles needed to complete labors for his cousin Eurystheus as a punishment for his madness-induced murder of his family.
The gods of Mount Olympus made Herakles subservient to Eurystheus, who asked him to perform 12 tremendously difficult tasks.
These labors were meant to be a form of atonement for Herakles' sins.
One of Herakles' labors was to kill the Nemean lion and take its skin.
This feat is depicted in various sculptures and art forms.