"It's sheer perfection. My precious G-virus. No one will ever take you away from me. " - William Birkin, Resident Evil 2
Dr. William Birkin is a character from the Resident Evil video game franchise. He was one of the Umbrella Corporation's top viral researchers and the man responsible for the development of the G-virus. He is also the man foremost responsible for bringing about the destruction of Raccoon City. Once a normal human being, he injected himself with the G-virus and transformed himself into an ever-changing mutant abomination.
Birkin joined Umbrella at the young age of 16, quickly rising to become one of the company's leading virologists under the tutelage of James Marcus. While working at the Umbrella Research Centre, he developed a friendship and rivalry with Albert Wesker and the two of them aided Marcus in his discovery of the T-virus. After the centre was closed down in 1978, the pair were transferred to the Arklay Laboratory as the facility's chief researchers. During their time there, the pair conducted extensive study into the Ebola virus and were introduced to Umbrella's first long-term test subject: Lisa Trevor.
In 1981, Birkin also met Alexia Ashford, a child prodigy who had joined Umbrella at just 10 years old. He loathed her and felt threatened by her unnaturally high intellect, quickly developing a competitive rivalry with her which was maintained until she used herself as a test subject for her T-Veronica virus, upon which she was placed in cryogenic stasis at Umbrella's Antarctic base.
By 1988, Birkin had married fellow researcher Annette and the couple had a daughter, Sherry. It was in this year that Umbrella president Ozwell E. Spencer had declared his old friend and company co-founder James Marcus as a liability and ordered Birkin and Wesker to assassinate him. With Marcus disposed of, Birkin was credited for all of his mentor's work on the T-virus.
Birkin's greatest triumph would come when he conducted an experiment on the mutated Lisa Trevor with an NE-α Type parasite to see if Lisa would accept the creature. While the NE-α experiment was a failure, it led to Birkin making an even greater discovery. The variation of the Progenitor virus that was injected into her in 1967 had absorbed all the mutagenic organisms that she had been implanted with since then and mutated into a new virus, which Birkin named the G-virus.
In 1991, the Birkins were transferred to Raccoon City to take charge of Umbrella's underground NEST laboratory. From there, Birkin conducted all of his G-virus research and bribed the Raccoon Police chief Brian Irons to cover up the project, using his wife as the "middle man".
During the events surrounding the T-virus outbreak in the Arklay laboratory, the Research Center, and the Ecliptic Express, Birkin and Wesker were shocked to learn that Dr. Marcus was somehow alive and responsible for leaking the virus. Knowing that his career would be over if the truth behind the old conspiracy ever came out, Birkin found and activated the Training Facility's self-destruct system destroying all evidence of his involvement in the decade-old "conspiracy", as said by Wesker.
In September 1998, Birkin completed his research on the G-virus. While he had originally planned on using it to elevate himself to Umbrella's executive board, he began to disagree with the company's policies and decided to keep the virus to himself with the intention of selling it to the US government. Umbrella sent one of its Security Service units to retrieve the virus before the government could extract Birkin. After a tense standoff, the USS fired on Birkin and mortally wounded him before taking an attache case filled with T and G-virus samples.
As he lay dying, Birkin used the last of his strength to remove a hypodermic syringe filled with G-virus from his labcoat pocket and inject himself with it. The virus saved his life as it rapidly healed his wounds, but mutated him into a savage, violent creature. The enraged mutant then proceeded to hunt down the USS operatives that stole his work, attacking them down in the Raccoon City sewers and viciously ripping them to shreds. The attache containing the viral samples was broken open in the struggle and Birkin, in his virus-fueled mania, ingested the G-virus samples. However, as he attacked the USS operatives, he also shattered the vials containing the T-virus. The T-virus spilled into the sewers and would be carried up to the city above by rats, sparking the chain of events that would go down in history as the Raccoon City Destruction Incident.
Several days into the Incident, on September 29th, Birkin had wandered into the Raccoon Police Department. Now driven completely by the virus, he sought only to propogate and spread the infection. The few survivors he encountered were incompatible with his parasitic spawn since they did not share his bloodline, and so the monster sought out Sherry, William's daughter, who had gone into hiding as the situation in Raccoon City deteriorated. As the deformed thing that used to be William prowled the city, it encountered survivors Leon Kennedy and Claire Redfield who fought against it. With each of these encounters, the monster would continue mutating and changing its form, before long losing any and all resemblance to a human being.
In his hunt for Sherry, who was the only compatible host for the virus in his body, Birkin followed Leon and Claire into the Umbrella lab complex beneath the city. The two survivors had encountered Sherry at the RPD and taken her under their protection as they searched for a way out of Raccoon. Inside the laboratory, Birkin confronted not only Leon and Claire but also the spy Ada Wong and his own wife Annette, who had produced a G-virus vaccine in order to give to Sherry. William was able to infect Sherry, but Leon and Claire gave the girl the vaccine they acquired from Annette before William killed her.
As the lab complex was counting down to self-destruction, Leon, Claire and Sherry boarded the Alexi 5000 escape train that would take them out of the lab and outside the city border. Birkin, who continued to mutate, pursued the survivors and boarded the train. The presence of the G-virus activated the train's own self-destruct device, forcing the survivors to stop the train before it reached the end of the tunnel and escaping on foot. By this point, Birkin had transformed into an enormous, oozing mound of flesh that was almost completely immobile, and so could not continue pursuing its quarry as they fled on foot out of the tunnel. The train then self-destructed and the explosion finally killed Birkin for good.
As a first-generation G, Birkin was driven to seek out compatible humans to breed with and spread the virus. Unlike the spawn he produced from incompatible hosts, he would continue to mutate and grow constantly, the virus continuously regenerating his cellular structure. As such, Birkin was biologically immortal and may have lived indefinitely had he not been destroyed by Leon and Claire. One can only speculate how much Birkin would mutate and grow had he been left unchecked.
In his intial mutant form, William still looks somewhat human. The left side of his body looks almost unchanged, but the right side has grown and warped to absurd proportions. A large stump protrudes from the right shoulder and the upper arm is dominated by a large eye-like organ that continuously shifts in its socket. This eye remains a constant feature as Birkin continues to mutate and other eyes will also appear across his body over time.
When Leon and Claire first encounter Birkin, he attacks them by wielding a large steel pipe. He moves slowly but packs a heavy punch. The eye on his shoulder is his weak spot.
Birkin becomes taller and his right arm now sports a set of menacing claws similar to a Tyrant. The left arm has become more muscular and a third arm appears to be growing out from the lower torso. A new head has grown with decidedly inhuman features; Birkin's original head can now be seen sinking into the chest.
Birkin is faster in this form and possesses strength similar to a Tyrant, so automatic weapons or grenades are the best tools to deal with him. The giant eye in his shoulder remains his main weak spot.
Birkin's third form seems to have gained a semblance of stability, though it now has two disproportionately large arms ending in razor-sharp talons extending from its back. The back arms are actually his original arms, the semi-human arms on either side of his torso being new limbs grown by the virus. The eye on his shoulder appears to have shrunk somewhat and another eye has appeared on his left hip. Birkin's face has completely disappeared and the new head appears to have an exterior skull. What appears to be some kind of maw is forming on his chest, the multiple boney spikes actually being fangs.
Birkin's attack range is increased in this form, his back arms having impressive reach. He can easily slice prey apart or impale them with his talons and can even partially "eat" victims with the strange maw in his chest.
Birkin no longer remotely resembles a human being when he reaches his fourth phase. He has transformed into a hexapedal beast with an elongated head and maxilla to accommodate the spiky maw on his front. He has an eye on the shoulder of his two large front limbs, though whether or not he actually sees through them is unknown.
Using its large forelegs and squat hind legs, the Birkin creature can charge and pounce at enemies with surprising speed, using its spiky mandible and central arms to tear victims apart.
Birkin's final form is a shapeless, oozing mass of flesh, fangs and tentacles. It is almost immobile, using its tentacles to slowly drag itself toward its prey. It absorbed firepower like a sponge soaks up water and was only finally destroyed when the Alexi 5000 train exploded. It is unknown if Birkin could have continued mutating following this transformation. According to a report by Albert Wesker, the G-virus would have continued mutating its host's cell structure indefinitely, so it could be that Birkin would have continued growing to gargantuan proportions.