|Affiliation||Hazardous Environment Combat Unit|
|Date of Birth||Unknown|
|Equipment||Night vision goggles, Powered combat Vest (P.C.V.), full-facial gas mask|
Adrian Shephard, 22 years old, is an HECU US Marine Corporal that had been assigned to the Black Mesa Research Facility to clear the base of any known threats, including any surviving witnesses, notably Gordon Freeman. Shephard's task had been cut short, and he soon finds himself fighting for his life rather for the HECU succeeding the events of the Resonance Cascade.
Compared to other marines, Shephard joins with the cynical scientists and security guards in order to make it out of the base alive. Though his overall mission was to silence any witnesses, he did not since his transport was shot out of the sky, before his commander can inform him on his objectives.
Along with Gordon Freeman and Alyx Vance, the cryptic G-Man takes great interest in Shephard's character and abilities. Concluding the events of Black Mesa's destruction, the G-Man argues for the survival of Shephard's life, displaying a remarkable amount of respect and gratitude towards his capabilities.
Opposing Force was the only Half-Life installment to feature Adrian Shephard, preserving a large quantity of fans. Valve Corporation's Gabe Newell stated that he may one day return into the series.