"Ritual skull cups are traditionally formed from a human skull that has been cut into shape, lined with a metal rim and ornamented.
Many skull cups are simply made out of a precious metal in the form of a cranium.
They are usually elaborately decorated with artistic designs and Buddhist symbols like lotuses and vajras.
Many are fitted with ornamented lids and have feet or a separate base in the form of human skulls.
As the libation vessel of a Vajrayana Buddhist, the skull cup can be seen as a parallel of the clay pot (kumbha in Sanskrit) of the Vedic sacrifice, the alms bowl of the Buddha, and the sacred water vase (kalasha in Sanskrit) of the bodhisattvas. In addition, as a receptacle for sacrificial offerings presented to wrathful deities, the skull cup parallels the tray of auspicious substances like jewels, flowers, or fruit presented to peaceful deities. In its most benign symbolism, as the begging bowl or food vessel of an ascetic, the skull cup serves as a constant reminder of death and impermanence.
When used for esoteric rituals, the history of the cranium's original owner has an important bearing on its ritual potency. The skull of a murder or execution victim is believed to possess the greatest tantric power; the skull of one who has died from a violent or accidental death, or from a virulent illness, possesses a medium magical power; the skull of a person who died peacefully in old age has virtually no occult power. Having great potency are the skulls of children who died during the onset of puberty or were born from the forbidden union of castes, out of wedlock, from sexual misdemeanor, or particularly from incest. The vital force or potential of the skull's previous owner is embodied within the bone as a spirit, rendering it as an effective power object for the performance of rituals.
In the ritual, lamas and other advanced practitioners drink consecrated alcoholic beverages or sometimes even blood from the skull cup, symbolizing the wrathful deity drinking the blood of his or her victim".http://www.michaelparenti.org/Tibet.html
What You think about this???