The Twelve Trials of Hercules include a journey to the underworld to bring back the triple-headed hound of hell.
The descent to the underworld symbolically represents the incarnation of the soul into a human life. The triple-headed hound of hell is a symbol of time—past, present and future.
The first of the monster’s heads is that of a wolf, which, like the past, drags its prey into the darkness. The second is that of a lion, which, like the present, leaps upon its victim in one awful second. The third is that of a dog, which forlornly looks up to its master in the same way that we look to the future with a desperate hope of better things to come.
This myth teaches that the hero must overcome time if he is to find the eternal oneness of God and escape the Grievous Wheel.