Butcher's Nails - Angron's Secret: After Angron was teleported away by the Emperor from Nuceria he was later examined aboard the War Hounds' flagship Adamant Resolve's Apothecarion by Vel-Kheredar, the archmagos veneratus of the XIIth Legion and a representative of Kelbor-Hal, the Fabricator-General of the Mechanicum of Mars.After ordering the XIIth Legion's Techmarines and Apothecaries away, the primarch was rendered somnolent by the psychic touch of Malcador the Sigillite.Vel-Kheredar examined the Nucerian archeotech neural implants hammered into the primarch's skull over the course of seven solar hours, all under the Sigillite's watchful eyes. The archmagos discovered that the Butcher's Nails had remapped Angron's brain after the device's implantation.When the Nails activated, they reduced the production of the neurotransmitter known as serotonin in the subject's brain to encourage instinctive aggression, just as they deadened emotional responses and electrical activity to any other portion of the brain save for that which regulated the flow of adrenaline.Unfortunately, the malignant archeotech device had not been designed for the biological complexity of a primarch's brain, as it eroded mental stability and slowly damaged the subject's capacity to reason.The implants also impinged on higher brain function by rewriting emotional responses. To make matters worse, removing the Butcher's Nails would only result in the death of the primarch by destroying his central nervous system.Over time, the Butcher's Nails would cause rapid cortical degeneration and eventually kill the primarch. This was a certainty, though Angron's transhuman physiology would continue to try to heal the damage as the Nails bit deeper.Vel-Kheredar did not know how long it would take the Nails to kill the primarch based on the little data available but he made an educated estimate.The archmagos reported these findings to the Emperor, and soon received a marked and sealed scroll with the Palatine Aquila upon it, handed to him by the Sigillite himself.It was a message from the Emperor's own hand. He ordered the archmagos to sequester his findings and to remain silent about what he had discovered.At this time, the XIIth Legion was in terrible shape, as they had been one of the last of the Legiones Astartes to find their gene-sire. The Legion's morale was low.It was bad enough that they were burdened with the only primarch to fail in conquering his homeworld. If they discovered he was doomed to die before the Great Crusade's end, it would annihilate what little morale remained amongst the Space Marine Legion then still known as the War Hounds.At a later point following the rediscovery of Angron, the famous Mechanicum technoarchaeologist, Arkhan Land, was brought to Terra and sequestered in one of the Emperor's secret, sacred laboratories at the heart of an inactive volcano in a region of extensive tundra.The Master of Mankind required Land's expertise in aiding His continued investigation of Angron's cortical implants while the primarch lay in an induced unconscious state. Land had gained previous experience with this archeotech device, known as a Cruciamen, during his expedition into the Hexarchion Vaults on Mars.The lore that had been contained within had represented a moral threat to Mankind, including knowledge that would allow a potential perversion of Human cognition. The Hexarchion Vaults had been resealed by the Emperor's own decree, ratified by Fabricator-General Kelbor-Hal and all Land's findings within had gone unrecorded.Land had seen the name of this ancient device within the profane texts in the Hexarchion Vaults, but had never actually seen one implanted and made operational, and never one of the specific pattern and intensity implanted in the primarch's brain in either stasis or storage.The devices similar to the Butcher's Nails in the sealed vault on Mars were more crude than the Nucerian construct.With the alterations made by the Nucerian device to Angron's limbic lobe and insular cortex, the Nucerian psychic-surgeons had impaired the primarch's ability to regulate any emotion at all. Furthermore, the Butcher's Nails had rewired Angron's brain so that he no longer had capacity to take pleasure in anything but the sensation of anger.Only neurochemicals and electrical signals related to rage and anger flowed freely through, and from, Angron's brain. All else was either dulled to nothingness or rewired to inspire a supreme degree of agony.It was a testament to the durability imparted to the creations of the Emperor's Primarch Project that Angron had managed to survive as long as he had.Because of these neurological changes, everything caused the primarch pain. Thinking. Feeling. Even breathing. The only respite Angron had was in the pleasure he now received from the neurotransmitters which carried anger and aggression.This rewriting of his neurophysiology certainly hindered Angron's higher brain functions, for the device had been cunningly wrought for a technology so crude.Land inquired of the Emperor whether He could remove the device from Angron, and the Master of Mankind replied that it was possible. However, the tendrils of the Nails bit deep, and had taken root in the meat of the primarch's brain, threaded through the central nervous system, and now passed in roughly serpentine coils down around the spinal column.Even worse, Angron's limbic lobe and insular cortex had been more than just savaged by the device's insertion; they had been surgically removed even before the technology's implantation.The device hammered into Angron's skull hadn't ruined those sections of his brain -- it had replaced them outright. In truth, those sections of the implant had effectively replaced those essential portions of the primarch's brain and were now the only things keeping Angron alive.Though the primarch's lifespan and tactical acuity had been reduced by the implant, the Butcher's Nails amplified his combat effectiveness in other ways to compensate.Since the primarch was thus still able to lead warriors in combat, the Emperor decided that He would return Angron to his Legion. Despite what had been done to him, a compromised primarch was still a primarch, and the Master of Mankind believed that Angron would still be able to fulfill his purpose as one of the Emperor's generals.