Gregor met his own first pupil, Alec Hill, in 1756.
In 1883, Gregor was living in the Pacific Northwest trying to help prospectors during a cholera epidemic. When one of Gregor's patients, a young boy, died from the affliction, the boy's father flew into a rage of grief, and gunned Gregor down. Duncan was on hand to cart his pupil off, to revive in private, but Gregor began to feel his first pangs of disassociation from mortals at that time. He kept his personal doubts from MacLeod, knowing his teacher would be the first to chide him.By 1992, Gregor had become a photographer, and a hardened cynic, having seen much suffering and pain over the years. At an exhibition of his work, he was reunited with Duncan, who introduced him to Tessa and Richie. Duncan was disturbed by Gregor's work. Tessa was further disturbed by Gregor's reminders that one day she would grow old and die, and Duncan would move on to another lover.
Duncan, distracted by a chance meeting with his own former lover, Linda Plager, failed to notice Gregor's behavior. Most disturbing of all, Gregor began to bait Richie, striking up a friendship at first, but then asking him what it would be like if he were immortal (obviously aware of Richie's nascent immortality). After Gregor nearly caused Richie's death in a botched motorcycle stunt, MacLeod angrily confronted his former student, accusing Powers of becoming suicidal and nihilistic. Verbally spitting on his old teacher, Powers stormed off. In a fit of rage, he vandalized his own exhibit.When Gregor later turned up at Linda Plager's hospital room, intending to "put her out of her misery," MacLeod was waiting. An infuriated Gregor drew his sword, and attacked his mentor, Duncan easily blocked Gregor's attacks despite being unarmed. As the fight spilled onto the hospital rooftop, Duncan overpowered Gregor, seizing his sword and forcing Gregor to the ground. MacLeod delivered an ultimatum: Gregor could change, or he could die. Though he defiantly chose death, when Duncan raised his arm to strike the final blow, Gregor felt a long-lost burst of fear. Finally broken down, he surrendered to Duncan and agreed to seek help.
After the ordeal, Gregor learned a new appreciation for life. He decided to re-enroll in medical school, and resumed his practice.
Gregor's sword was an El Cid Tizona with an etched blade.
Gregor was intended to be the main antagonist in the season 3 episode Obsession. The premise was that Gregor had gone from one extreme to the next; from despair and fatalism to obsessed joy. But Wyman had a scheduling conflict, so the story was altered to use a different Immortal; David Keogh.
This plot line was similar to The Modern Prometheus, in which the jaded Immortal, Byron, who was Methos' last student, was also a self destructive fatalist and cynic. MacLeod had far less patience with Byron's nihilism than Gregor's, and in that case took his opponent's head, perhaps it was because Gregor had not yet caused the death of any mortals.
"If I take your head will I feel love, joy?"