The Mass of the Phoenix is a single person ritual within Thelema, a philosophy and religion created and organized by author and occultist Aleister Crowley. The Mass was first printed as Chapter 44 in Crowley's The Book of Lies, published in 1913.
Within this ritual, the practitioner consumes a Cake of Light (a wafer made from meal, honey, olive oil, Oil of Abramelin and blood/bodily fluids).
Mass of the Phoenix Wikipedia
Critics of this ritual often cite the cut that the practitioner makes on their chest as self-mutilation. The practitioner does not have to slice into their skin and draw large amounts of blood. Lon Milo DuQuette wrote that "nowhere is it indicated that pain, scarring, or injury is a required element of the ceremony." The practitioner need only scratch their skin lightly and increase the pressure enough for a tiny droplet of blood.
There are also those who consider doing the ritual astrally (within their minds). Some consider this a safer and more practical alternative to marking their skin. Although the legitimacy of this method is questionable, it is still to be considered.
Although the Cakes of Light are famous for sometimes having semen or menstrual blood within them, using these bodily fluids is not a mandatory part of their creation. Within The Book of the Law, the instructions for the making of a Cake of Light are found:
For perfume mix meal & honey & thick leavings of red wine: then oil of Abramelin and olive oil, and afterward soften & smooth down with rich fresh blood. The best blood is of the moon, monthly: then the fresh blood of a child, or dropping from the host of heaven: then of enemies; then of the priest or of the worshippers: last of some beast, no matter what. (AL.III.23-4).
Various types of blood are given as acceptable within a Cake of Light. "Of the moon" refers to monthly menstrual blood. "Of a child" refers to fluid from sexual intercourse. "From the host of heaven" refers to semen. "Of enemies; then of the priest or of the worshippers" is self-explanatory. "Last of some beast" refers to animal blood; the least controversial since many foods are made with the substance. Although the first three options are used for their higher value (and notoriety), any option is acceptable.