Augeas

[1] He is known for his stables, which housed the single greatest number of cattle in the country and had never been cleaned, until the time of the great hero Heracles.

The derivative adjective augean came to signify a challenging task, typically improving or fixing something that is currently in a bad condition.

[2][3] Augeas's lineage varies in the sources: he was said to be either the son of Helios[4] either by Nausidame[5] or Iphiboe,[6] or of Eleios,[7] or of Poseidon, or of Phorbas and Hyrmine.

Eurystheus intended this assignment both as humiliating (rather than impressive, like the previous labours) and as impossible, since the livestock were divinely healthy (immortal) and therefore produced an enormous quantity of dung (ἡ ὄνθος).

According to the odes of the poet Pindar, Heracles then founded the Olympic Games: the games which by the ancient tomb of Pelops the mighty Heracles founded, after that he slew Kleatos, Poseidon's godly son, and slew also Eurytos, that he might wrest from tyrannous Augeas against his will reward for service done.