The grey energy emitted by corpses and dead tissue is referred to by the titles of Death Energy and the Death Essence, and the variant of witchcraft incorporating it is referred to as Death Magick.
It is known to be a necessity for the witch to develop and attunement to the Death Essence prior to engaging in Necromancy, but the aspiring Necromancer is always warned not to allow the Death Essence to seep into her aura, less her health become diminished. Nonetheless, some amount of Death Energy always infiltrates the subtle body, and so a gradual debilitation continues.
There is a powerful loophole to this guideline which few magickians are aware of: a magickian who has acquired a proficiency in the practice of psychic vampyrism will have developed such an aptitude for digesting and altering foreign energies that she becomes capable of not only imbibing the Death Essence without harming herself, but even benefiting from the act.
I refer to the act of becoming saturated with the Death Essence as “entering the Mortis State.” To do so is to become magnified in power and undergo permutations of the very essence. The magickian becomes gradually likened to the entities which she interacts with by way of gradual permutation, and for the vampyric magickian, the alchemy of Death Magick and communion with the dead develops the psychic senses, renders the Kundalini easier to raise, causes the bestial manifestation of the Higher Self to be more easily accessible, and permutates the chakras such that working with them yields greater and quicker results.
In the Mortis State, the sorceress is more capable of perceiving the astral oddities about her and retrospectively remembering dreams. The magickian who is saturated with the Death Essence is more difficult to kill and less likely to die. Sometimes, a vampyric magickian can feed on the Death Energy within a moribund person, and in doing so, save their life.
I refer to the magickian’s aptitude for deprogramming exogenous human energy and attuning it to one’s natural ‘flavor’ by the name vampyric metabolism. By regularly feeding on the prana of other humans, the magickian develops the vampyric metabolism, increasing her aptitude for energy work in general, and making her suitable for the art of self-transformation via Death Magick. Of all the countless avenues of spiritual progression available to me, my spirit guides told me that Necromantic Alchemy was among the very most useful and essential to my ascent.