Heracles' Twelve Labours as Atonement
Driven mad by Hera, Heracles killed his own children, and the Delphic oracle sent him to serve his lesser cousin Eurystheus of Tiryns and perform whatever labours were set. The tasks included killing the Nemean Lion, cleansing the Augean Stables by diverting rivers, and fetching Cerberus from the Underworld. Eurystheus disallowed two of the ten labours first set, because Heracles had help with one and took payment for the other, so the count rose to twelve and his penance grew longer.