Corporal Adrian Shephard is a US Marine Corporal[1] assigned to the Hazardous Environment Combat Unit from the Santego Military Base, Arizona, where he was trained by Drill Instructors Dwight T. Barnes and Sharpe, and the protagonist of Half-Life: Opposing Force.

He is one of the soldiers sent to the Black Mesa Research Facility to eliminate the Xen invaders. Shephard, however, is not aware of his classified mission to silence the witnesses, especially a scientist named Gordon Freeman