Gregory Farrell is a member of the United States Military's Delta Force.
Gregory Farrell was identified in the U.S. / U.K. Motor Neuron Rapidity of Response tests as having extraodrinary reflexes, making him one of the few people who could disarm the CincLock-VII security system.
Farrell and another Delta member, Dean McCabe, were tasked to the abandoned Soviet Krask-8 facility in Siberia on a mission to liquidate some Islamic Chechen forces who has apparently taken control of the nuclear ICBMs stored there, with Shane Schofield intended to arrive as backup.
Soon after they arrived at Krask-8, Farrell and McCabe's teams were ambushed by Executive Solutions, and both Delta leaders were decapitated to claim the price on their heads, as part of a group of billionaires called Majestic-12s plan. Soon after the Marines arrived at Krask-8, Bull reported finding Farrell's headless body to Schofield, and as Schofield's team had found the also headless body of McCabe, Schofield realised the mission was a set-up.
After Schofield managed to escape from the Ex-Sol forces, Farrell's head, as well as McCabe's, were taken to the Forteresse de Valois so that Ex-Sol could claim their bounties.
Schofield later took revenge for Farrell and McCabe on Cedric Wexley by crushing his head under a door.