Hercules final labor was to capture Cerberus, the three headed dog that guarded the underworld. Hercules got permission to take Cerberus from Hades, but Hades told him he could only have him if Hercules subdued him without using any weapons.
Atlas was the son of the Titan Iapetus Clymene. He married Pleione who bore the seven sea deities with the name of the Pleiades Nymphs with the name "Hesperides", also known as the "Daughters of Evening". Unlike his brothers he fought with the other Titans supporting Cronus against Zeus. Due to Cronus's advance age Atlas lead the Titan's in battle. As a result he was singled out by Zeus for a special punishment and made to hold up the world on his back.