Hercules in the Underworld
Nessus, Hades, and the Cerberus all play into the labors of Hercules, although not in the fashion portrayed here.  The capture of Cerberus was supposedly the last labor of Hercules where he brings Cerberus to the surface world at the demand of King Eurystheus, not a request of Hades.  He returned Cerberus to Hades only after the twelfth labor was completed.