Why must the region ruled by Hades have been a very gloomy place?

The region ruled by Hades, known as the Underworld in Greek mythology, is often depicted as a gloomy place due to its association with death and the afterlife. This realm was characterized by darkness, shadows, and a somber atmosphere, reflecting the sorrow and finality of mortality. Additionally, the presence of spirits and souls in a state of longing or despair contributed to the pervasive sense of melancholy. The stark contrast to the vibrant world of the living further emphasized its dreary nature.