Chod means cutting, and what is to be cut is the grip of self. The practice, in outline, is this: the practitioner goes to a place that frightens people, a charnel ground, a mountain pass, a spot known for demons, plays a drum and a thighbone trumpet, and formally invites every hungry, harmful and afflicted being to come and eat. Then, in visualisation, the practitioner's own body is separated from consciousness and offered as the meal.
The theatre of it is what people remember and it is the least of it. The doctrinal ground is the Perfection of Wisdom, the teaching that the self, the body and the demons are all empty of any independent existence, and the point of the exercise is to test whether that teaching has actually been absorbed or merely learned. The demons that matter, in Machig's own analysis, are not the ones in the dark. They are the internal ones: attachment, aversion, and above all the pride of the practitioner, which she treats as the hardest of the four to cut.
Chod cuts across the Tibetan schools rather than belonging to one, and its liturgies are still practised. The atlas describes the practice and does not set it out as instruction: the tradition transmits it through a teacher, with preparation, precisely because the exercise is designed to be destabilising.