What is the moral of the story of Hades?

Hades is often depicted in myths, though not as often as the more well known gods and goddesses, and the theme is usually that what belongs in the Underworld stays there and this comforted the people of ancient Greece who believed in all sort of spirits from the vengeful to the ghosts who sent dreams of prophesy to the living. It also depends upon what the individual gains from hearing the myths.