Death Feedback is an inborn genetic reflex that prevents humans from harming other humans.
- An ethologist called Konrad Lorenz who lived during the peak of the previous civilization said that powerful animals like wolves and ravens, as well as social animals, have an innate mechanism that causes them to avoid conflict with members of their own species. This is called attack control. On the other hand, physically weaker animals like humans and rats do not have as much control and tend to fight among each other, to the point of violent massacre.
- If Cantus users were to live together in society, a powerful restraint on violence was essential. The only effective way was to alter the human genome. Wolf DNA was decoded and the gene responsible for attack control was isolated. Yet just that was not enough. Something that could suspend their ability to attack was also necessary. Two mechanisms were inserted into the genetic code. The first was regular attack control identical to the wolves', the second being called "death feedback".
- In the beginning, they came up with "conscience feedback", which would disrupt a person's concentration when they wanted to attack someone with Cantus, to complement the attack control mechanism. However, the results were inconsistent, so they were unable to use it in the real world. Its replacement was the simple yet effective "death feedback".
- Death Feedback operated on the following principles; When the mind recognizes that the user is attempting to harm another human, their Cantus subconsciously activates and stops the functions of the kidney or parathyroid. This results in symptoms such as discomfort, heart palpitations, and sweating, which can be intensified through education, conditioning, and hypnosis. At this stage, most people would stop attacking, but if they continued, tetanic asphyxia caused by low blood calcium, or cardiac arrest caused by a rapid spike in potassium concentration would kill them.