And in general, this is true with a particular point of view. Bhairava embodies the dreadful nature of Shiva, par excellence; his name is enough to testify this. Born out of his destructive anger, he is the personification of the exterminating function of Rudra in the Trimurti. About ambiguity of Bhairava's figure I wrote a little here or there, but this is never enough. Rudra's manifestation in Bhairava form became central to the shaiva traditions related to the kApAlika branch of the old pAshupata form of the shaiva-shAsana known for understanding and accepting this symbol literally. Nevertheless, the skull as such powerful symbol for anyone, has a lot of other hidden meanings (it is the set of meanings, not one).
Maharakta GanapatiApropos, the skull it is one of the principal practice supports of the Vajrayana yogin. Many of the deities of Vajrayana, including Mahasiddhas, Dakinis and Dharmapalas are depicted carrying a Kapala, usually in their left hand.
VajrayoginiThe buddhist skull cup Thod-pa is used in tantric ritual practices to represent the transformation of delusion into perfect wisdom. The skull also symbolises Great Bliss and is a potent symbol of impermanence.
Many ancient cultures retain special attitude to this symbol and primary, it carries the human mortality idea but in an important memento mori reminder. Because in the face of death that man's self-aware is born.
This is a very common symbol in Christianity for to pondering the earthly reality of our mortality and the eternal truth of the spiritual life. It was not unheard-of for medieval religious to keep a human skull about to aid them in their meditations.
For the medieval alchemist, the skull symbolized purification from the false identity or poisoning ego that fights desperately for its survival but must be devoured in the flames of higher consciousness. Or for the ancient Celts, it was the seat of the soul. This theme is persistent throughout Celtic spiritual life and the symbol of the severed head may be regarded as the most typical and universal of their religious attitudes.
It can be continued but the quick-list of kapala symbolism include: Time and Time's overcoming, Temporary and Eternal, Power, Divinity, Gateway, Creation, Initiation, Concentration and so on. All these symbols, or supports, or tantric rituals can serve as tantric meditations to achieve a transcendental state of thought. Exactly, this is their direct appointment. The unfathomable figure of Bhairava holds all these meanings so far as we can understand it. But it brings us closer to an understanding of not only of impermanence, but also of spiritual awakening, the death of the false self, the Great Death. It means that one sees into one's own Nature, into the One that is neither born nor destroyed. When it brings all back to One. When the amR^ita-sravaNa nectar starts flowing from within the skull.
Om Bhairavaya Namah