Skull Cup
The skull cup, known as kapala in Sanskrit, is made from the upper section of a human cranium. The skull of a murder or execution victim contains almost the strongest magical powers. Anyone who has died a violent accidental death or disease is not as powerful. Someone who has died of old age possess no magical powers at all. But where as a child going into puberty has a very strong potential  potency as do children born from forbidden marriages, and children born of rape and incest victims. The skull of these children between the ages of seven or eight are considered to contain the strongest magical powers for tantric rituals. The reason being the life force of the deceased is embodied within the bone in the form of a spirit.
The skull cup is a reminder of death and how transitory life is. It is used to place offerings in for evil spirits or demons.
During one of the rituals the cup is held level with the heart, and then a curved knife is held above the skull cup. The knife is used to sever the main arteries as well as the vital organs of the demons, and these are collected as sustenance.