It can be interpreted as something that is symbolizing death, mourning and darkness. The darkness could also be interpreted as the color black which is the synthesis of all colors and it is symbolizing virginity. Keep in mind that darkness almost all of the time symbolizes unknown and scary aspects of your personality or the fears you have since your childhood. The depression is also marked always with the color of black. Some people are mourning in their waking lives, therefore they dream about the darkness where they loved ones have gone.
Read more about dreaming of Darkness in other dream meanings interpretations.