Germaine Macks was an Arbitrator stationed on Gershom and was tasked with killing a mysterious creature that was preying upon the population in Outer Udar. However she was unable to even locate the creature and the predator continued its rampage. Much to her annoyance, the fearful population of Outer Udar, soon decided Macks was not capable of killing the creature and hired a group of off-world hunters led by Fernal Skoh. However when they too failed to kill the creature, Baron Karne contacted Gershom's Planetary Governor for aid in protecting his lands. The Governor was a personal friend of Karne and quickly tasked the Magos Biologis Valentin Drusher with aiding the Baron, but during their conversation there was a miscommunication as to what was expected of the Magos. When Drusher later arrived in Outer Udar, the Magos explained to the Baron that he was merely there to catalog the creature, in order to finally complete the listing of all of Gershom's fauna; which the Governor had contracted Drusher to do years ago. Despite this mix-up however, the Magos agreed to help in tracking the creature down and worked beside Macks and Skoh's hunters to end its threat to Outer Udar's population. Afterwards, the Magos began gathering evidence from the bodies of the predator's victims and learned that despite no one having been reported surviving an encounter with the creature, it was widely described as having no eyes. Skoh later told Drusher, that the description likely spread from the fiery sermons that the Outer Udar's Ecclesiarchal Bishop had started to give, after the predator had begun its attacks on the population. The Bishop claimed that the creature was an emissary of Chaos, that preyed upon them due to their lack of faith and it could only be killed after they reaffirmed their faith in the Emperor.
Despite this proclamation though, when the predator killed yet another victim, Macks and the others quickly traveled to the murder scene and began tracking the creature. However, the predator soon ambushed the group of hunters Skoh led and killed most of them before Macks, Drusher and the Junior Arbitrator Lussin found them. The lone surviving hunter of Skoh's group subsequently fled, but Skoh lived long enough to warn Drusher that the mysterious predator was a Tyranid, before he then died from his wounds. Luckily one of the hunters had been able to hit the creature with a tracker during the ambush and Macks' remaining group continued to hunt it. They were able to track it down to an abandoned water-mill, but the creature launched yet another ambush and quickly killed Lussin. It then turned upon Macks and Drusher, who each saved each other's lives in battle with the predator, before the Arbitrator finally killed the creature. Drusher then examined its corpse and confirmed that Skoh had been right, the deadly predator they had been hunting was a Hormagaunt Tyrannid. Further examinations by the Magos, led to the discovery that the Hormagaunt had been implanted with a goad-control, that had allowed someone to use the creature to commit the killings. When Drusher informed Macks of this, the Magos speculated that the Outer Udar's Bishop had been behind the attacks; as he had a lot to gain from something that would reinvigorate his stubborn flock's faith in the Emperor. Macks would later take part in the full-scale investigation that was then launched, to determine who had been behind the Hormaguant's attacks.