Sisyphus

In Greek mythology Sisyphus was the king of Ephyra (now Corinth).

He was punished for his self-aggrandizing craftiness and deceitfulness by being forced to roll a boulder up a hill, only to watch it roll back down, repeating this action for eternity. Sisyphus promoted navigation and commerce but was avaricious and deceitful. He killed travelers and guests, a violation of xenia, which fell under Zeus's domain. He took pleasure in these killings because they allowed him to maintain his iron-fisted rule.

Persephone supervising Sisyphus in the Underworld.

Hades with Cerberus - Pluto Carricci painting

Sisyphus's greatest triumph came at the end of his life, when the god Hades came to claim him personally for the kingdom of the dead. Hades had brought a pair of handcuffs, and Sisyphus expressed such an interest that Hades was persuaded to demonstrate their use - on himself. The lord of the Underworld was kept locked up by Sisyphus, which meant nobody could die. As a punishment for his trickery against the Gods, Sisyphus was made to toil endlessly.

The maddening nature of the punishment was reserved for him due to his belief that his cleverness surpassed Zeus.

His hubris ended up consigning Sisyphus to an eternity of useless effort. Pointless or interminable activities are described today as sisyphean.