These skull cups are used in Buddhist altars to offer wrathful divinities wine which symbolizes blood or dough cakes that are shaped into eyeballs or ears. During tantric visualization based on meditation and deep philosophical study, they go into a transubstantiation occurs and the wine transforms into wisdom nectar. This liquid will enlighten the mind of one or all the deities in the Celestial Palace of the Mandala. That is just one of the many uses of these skull caps during ritual culture.