Prior to the Caal invasion, Terry worked as a network administrator for a small-business association on Jennifer's Star. His rather unremarkable life was dramatically upset beginning with the Caal assault on his homeworld in 2264. Although they did not understand what was happening at the time, Terry, his family, and many of his friends were able to survive the invasion and escape possession by hiding in service tunnels and unfinished construction sites on the outskirts of Dynametro.
When the Caal eventually abandoned the planet for their invasion of Avalon, however, the survivors' celebrations were brief. Only a few weeks later, soldiers of Vin Dane's nascent Holy Terran Empire landed on the planet to "cleanse" it of any lingering Caal threat. Most of Terry's comrades who'd hidden from the Caal were killed by these holy warriors, their bodies incinerated with plasma weapons or burned in mass pyres. Eventually, Terry himself was captured along with the remnants of his family. But as he watched his parents being melted to the cheers of cult fanatics, Terry had a revelation that changed his life and destiny.
Although he had earlier believed the purge of Jennifer's Star to be just another mindless horror piled atop the trauma of the Caal invasion, as Terry looked into the flames of the latest funeral pyre, he suddenly realized that the cult was right. Indeed, he saw that his parents had been among those possessed by the Caal all along, and that it was the intensity of the Imperials' faith which prevented the wraiths from immediately taking new hosts. The power of his revelation and conversion was so great and so visible that the cultists and Imperial troops had no objections when he asked to be freed in order to join them.
Terry immediately abandoned his old life, even his own name, and never looked back. After assisting the Imperial forces complete their purge of Jennifer's Star, he took a recommendation from one of the cult leaders, and traveled to New Paris. There he became a monk in an abbey confiscated from a Catholic sect during the new cult's frenzied uprisings in the system. Although the abbot, Father Rourke, was happy to accept Terry in his assumed vocation as a "demon hunter", there was little need for such services. Instead, Terry spent the next few months training his body and channeling his faith and conviction so that he would be ready for the next time the Empire was confronted by infernal enemies. In the meantime, he became something of a model cultist within the abbey: kind and plain-spoken towards both his fellow monks and laypeople, including the unfaithful, yet absolutely convinced of the cult's righteousness.
Terry hunted and fought Scyr aboard the Utopia Planitia shipyards above Mars during the Ascension war, where he was critically injured after being sucked through an airlock.
After the war, and despite his incapacity, Terry accepted duty with an elite Imperial strike force tasked with hunting Caal. The new INS Nightmare brought Terry and the other trainees to the site of the original Battle of Avalon to learn to overcome Caal possession. The strike force proved to be a ruse: all of the recruits were being offered up to the Caal as new hosts.