The meaning of this statement is that the essence called nectar that is stored in the skull, symbolised by the fivefold objects of the world, constitutes the best kind of drink, which is technically called rasilsava the liquor of nectar on account of its ability to produce the highest kind of bliss. The skull is full of that nectar. In other words, the material portion of the world is symbolised by the skull as its outer covering or shell; the essence stored therein is the nectar capable of producing perfect bliss; hence it is said to constitute the best kind of drink. A skull is held in the hands of the spiritual adept who practices austerities. This has been indicated by the author in the above verse by the phrase the skull that lies in his hands.
The rays of consciousness symbolised by the 4akti power underlying the senses, such as the eyes etc., are the instruments for the enjoyment of objects. This has been stated in the verse by the words he drinks from the skull that lies in his hands Spiritual adepts are said to taste the nectar, the universal drink, through the senses which are in essence rays emanating from the skull which symbolises all the objects of experience in the world. This is the meaning of the verses. The spiritual adept always sucks through the channel of power inherent in his senses the nectar underlying all objects of experience, all of which he experiences as resting in his own pure consciousness bhairava.
He thus enjoys the integral unity of everything until he reaches the supreme goal. This constitutes the austerity for the spiritual adepts who serve the lotus feet of their spiritual master. All other austerities only dessicate and emaciate the adept’s physical bodies in the course of time. All that has been described above is summarised in the following verse in order to prove its superiority to other views: Having realised the supreme Being, named MaheSvara the great Lord, who is without birth and dissolution, he abides as he wishes, his aim fulfilled because of the manifestation of his nature as the knower. In the manner described above, the spiritual adept realises the supreme truth, MaheSvara, who normally remains hidden to ordinary mortals.