William G-3 / G-4
"William Birkin was a brilliant top scientist for Umbrella whose quest for unlocking the mysteries of genetics caused his own undoing. Birkin's research led to the perfection of the G-Virus, a virulent strain of mutagenic DNA, deadlier than the T-Virus, that causes unnatural but amazing cellular transformations when exposed to live organisms. When Umbrella sent in a team of assassins to obtain the G-Virus, Birkin was caught in the cross-fire. With his last dying act, he administered the untested G-Virus into himself, beginning his transformation from man to monster. As it courses through his body, the stages of the G-Virus alter Birkin, twisting him into a grotesque new life-form and endowing him with superhuman strength. His senses have become heightened and his very nature has become predatory."