In these two techniques, the 63rd and 64th verses from Vigyana Bhairava Tantra, Shiva says:
Visualize utter darkness
Of the nights of the waning moon
If you wish to see the Bhairava form
Close your eyes
Let the darkness spread
Become one with Shiva
Most people identify with light as good and divine energy. Shiva breaks the duality asking us to contemplate on darkness as energy, as Shiva’s energy. For many of us this will take some getting used to.
There are several interpretations of these verses as dharana techniques in the tantric tradition. Several form part of the aghori tradition of tantra, the word aghori itself representing darkness. Some refer to these as the left hand techniques, as opposed to the right hand techniques of yoga. Some believe that these inspired black magic. Any technique, of light or darkness, left hand or right hand, can be attempted to nurture and destroy. This is the constant juxtaposition of good and bad. Nature does not judge anything as good or bad. It just is. Rain nurtures. Floods can kill. Sunlight nurtures. Excess heat can destroy. Shiva creates and destroys as the rejuvenator.
Those of us who are visual love to experience colors while meditating. Not many would be satisfied with pitch darkness. That would connote bad omen. Shiva says it connotes him.
Some techniques based on this dharana visualize one’s energy rising through the two energy pathways ida and pingala that wind around the chakra energy centers. Ida represents the lunar, feminine and dark energy while pingala represents the solar, male and light energy paths, both coming together with the central nadi sushumna at each chakra. It is said that aghori practitioners meditate on dark New Moon nights in cremation grounds, some on corpses, to obtain supernatural powers. It is best we stay from these interpretations.
I have practiced a variation of these techniques lying down visualizing I am dead, in shavasana, all limbs cold, darkness enveloping me, and experienced peace, with a release from all fears of the unknown including death. This helps to disengage from mind body conditioning.