Albert Wesker is one of the most popular villains throughout the Resident Evil series. Wesker's story begins quite early though. Even before the events of Resident Evil.
It all started with Project W (Project Wesker), which was set up by Ozwell E. Spencer, in order to create a league of "super humans" who would look to Spencer as a god and do whatever it is that he wanted. Ozwell named his project after the Umbrella official at the time. The project first started off by kidnapping kids who were born from parents with an above average intelligence. The children would be taught to do whatever Spencer says, they would also be trained in order to get them to a superior physical condition. The children were then injected with the Progenitor Virus. Most of the children died leaving very few. The surviving children were then monitored for the rest of their lives.
Shortly before the events of Resident Evil however, Albert Wesker worked for Umbrella at the age of eighteen. Wesker worked under James Marcus, and alongside William Birkin. Working in the Management Training Division, Wesker was deemed as a prodigy. Unfortunately, the division was shut down in 1978, causing both Wesker and Birkin to be transferred to the Arklay research facility located on the outskirts of Raccoon City. The two worked on the T-Virus for thirteen years with their research finally coming into play in 1988 with their creation of the Tyrant. Not to long after, they were ordered to kill their mentor, James Marcus, and acquire all his research. This incident along with Birkin's creation of the G-Virus by mutating Lisa Trevor, caused Wesker to lose his faith in his team. Wesker then transferred to the Umbrella Intelligence Bureau in 1991. In 1996 Wesker former the Raccoon City branch of the S.T.A.R.S. (Special Tactics and Rescue Service) acting as the leader and captain of the Alpha team. Being the best of the best it wasn't long before the team were considered heroes, the S.T.A.R.S. were then dispatched to the Arklay Mountains in 1998 to investigate what was assumed to be cult murders.
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Although Wesker is no longer apart of Umbrella's staff, he is still allowed into the facility beneath Raccoon City's sewers by William Birkin. Birkin needs Wesker to help him monitor an outbreak within an aboard train that both had a personal stake in. A small task force was sent in to clean up the train. At the end of the game Wesker decides to end all ties he had with Umbrella. Birkin gives Wesker an experimental virus, Wesker then continues his plans to lure S.T.A..R.S. into the Spencer Mansion, in order to collect combat data on Umbrella's B.O.W's (Bio Organic Weapons).
Wesker leads his team of S.T.A.R.S. members through the Raccoon Forest, filled with infected canines, into the Spencer Mansion which was suppose to be abandoned. Due to the well kept appearance of the mansion, the members were a bit baffled, being the fact that it was supposed to be abandoned. Wesker on the other hand, knew that Umbrella was using the mansion for research on their B.O.W's for years, and breaks himself away from the other S.T.A.R.S. Wesker takes this time to inject himself with the experimental virus given to him by Birkin.
With the S.T.A.R.S. progress fighting the B.O.W's Wesker still was not satisfied. He called in aid from S.T.A.R.S. Operative Barry Burton. He tells Burton that his family is being held hostage by Umbrella and would be executed if he did not follow his instructions. Barry being the family man that he is, reluctantly follows Wesker's directions.
Wesker's plans are going well until Bravo team Captain Enrico Marini finds a document linking Wesker to the Umbrella Corporation. These puts a huge damper on Wesker's plans causing him to nearly reveal himself and put a bullet in Enrico before disappearing into the shadows.
Wesker is encountered twice during the game, found on the cabi grounds being attacked by infected insects and finally at the end of the game where it is revealed that Wesker is not the person he makes himself out t o be. outnumbered by his former team mates, Wesker releases the Tyrant. Based on certain circumstances, waker is either knocked unconscious by the Tyrant or is impaled by it. If he is impaled the Tyrant activates the self-destruct mechanism in the lab. If Wesker is knocked unconscious his body can be found lying near the self-destruct mechanism after it has already been activated.
Either way esker is presumed dead after the explosion. However, Wesker comes bcd with super-human strength and agility, thanks to the virus Birkin gave to him. Wesker escapes the lab before it is destroyed by the explosion.
With everyone under the impression that Wesker is dead, he uses the opportunity to go underground and serve the Agency (Umbrella's Rival). During the confusion caused by the outbreak, Wesker hires Ada Wong to steal the remaining G-Virus from William Birkin's daughter Sherry. The operation was a disaster leaving the virus in the hands of H.U.N.K., an Umbrella Mercenary. Being the man that Wesker is, he refused to take no for an answer and retaliated by locking Sherry in a secret facility, thinking she knew more about the G-Virus.
While spying on Umbrella Wesker found out that a strain of the T-Virus was being developed, known as he T-Veronica Virus, created by Alexia Ashford on Rockford Island. The location of the island was secret to those outside Umbrella. Wesker still managed to launch an assault on the island along with other members of the Agency. Although the attack was a success Alexia managed to flee to the Antarctic Research facility. Wesker goes after her and ends up running into Chris Redfield (former teammate from the S.T.A.R.S. division). At this moment Chris is shocked to see Wesker alive and more powerful than before, at this time it is brought to light that Wesker never died during the explosion at the Spencer Mansion, and the Tyrant who attacked him. With Wesker becoming more powerful it had removed all conscience he had and has made him obsessed with destroying the world.
While on the island Wesker had tried to use his powers to defeat Alexia Ashford, but she in turn used her mutations from the T-Veronica Virus to fight back sending him fleeing. Of course before he makes his exit he says taking down Alexia was an order to Chris, leaving Chris to do his dirty work. Not willing to accept defeat, Wesker retrieves a sample of the T-Veronica Virus from Steve Burnside's body. While doing so Chris set off the self-destruct timer and while attempting to escape he runs into Wesker. Chris convinces Wesker to let his sister go as the two battle out their differences one last time. Wesker being the cocky man that he is accepts knowing that with his newly found power, Chris would be no match for him. As the two brawl, Wesker is in total control of the fight but allows Chris to jump to a lever which drops tons of iron orders down on him. Wesker immediately gets up from under the girders but at this time him and Chris are separated by a huge wall of fire. Chris and Claire manages to escape the facility as its being destroyed, at this time many believe that Wesker was killed once again.
In 2003, two years after the Code Veronica incident, Wesker broke into a Russian Unbrella facility in order to retrieve information from the Red Queen. While in the facility esker is attacked by Sergei Vladimir and his army of B.O.W's. Wesker has no trouble taking them out and soon comes face to face with Vladimir who has mutated into a variation of the T-003 Tyrants that he had been developing for Umbrella. In the end Vladimir was destroyed by Wesker.
Using the information he stole from the Russian base, Wesker had the umbrella Corporation liquidated. Wesker wanted to destroy Umbrella and rebuild it as he saw fit, not the way Ozwell E. Spencer wanted things done so in order to do that Wesker came in contact with the S Corporation. We don't know much about the S Corporation other than the fact that they have become the leading pharmaceutical company since Umbrella collapsed. The Agency being suspicious of Wesker's intentions, they hired Ada Wong to act as his operative during his affiliation with Los Illuminados and to supply him with a decoy sample of the Las Plagas Virus. Although the plan worked, Wesker knew the sample was a fake and sought the virus using other tactics.
Unsure of Spencer's intentions regarding the B.O.W's, Wesker spent a lot of time and money trying to find Spencer. Wesker soon found out that Spencer was located in a remote castle. Wesker was surprised to find that Spencer had in fact been expecting him. Spencer told Wesker about Project W and how all the training was leading up to Spencer proclaiming himself as a god, but Wesker was the only survivor. After receiving this bit of information Wesker realizes the only thing standing in his way of the control of a race of "super humans" was Ozwell himself. Wesker kills Spencer by plunging his hist through his chest (I really felt bad for the dude since he was old and in a wheelchair).
Ozwell wasn't even dead for five seconds before Jill and Chris came barging in and attempts to take Wesker down. Of course Wesker is more than a match for the duo and almost finishes Chris off for good. Thanks to Jill's brave attempts, she charges Wesker and the two crashes through a window falling off a cliff. Wesker nor Jill's body was found but both survived the fall. Wesker held Jill captive and experimented on her in cryo freeze to make her into an ally against Chris. Using the P30 strain of the Progenitor Virus, Wesker manages to gain control over Jill.
Meanwhile, Wesker decided to reopen Umbrella's African facility. While continuing his development of B.O.W.s and working with Tricell Pharmaceutical Company he had the means of reopening the African facility. Using the Progenitor Virus and Tricell's resources, Wesker was able to create Uroboros. Uroboros was a virus that had the capability of kiling all living beings with the exception of those who would use the virus to evolve into the next form of humanity. However, the virus was too poisonous and killed all the test subjects. Soon after a cure was developed due to Jill's powerful antibodies which were developed to combat the T-Virus she was exposed to in Raccoon City. Using her antibodies Wesker modified the Uroboros Virus and used B.O.W. smuggler, Ricardo Irving, to sell them on the black market in Africa.
Working with his partner, Exella Gionne (CEO of Tricell's Africa Division), Wesker spends most of his time harvesting flowers used by Umbrella in the 60's and 70's to make the Prognitor Virus and use it to make enough Uroboros to take over the world. Stocking the virus in missiles, Wesker planned on infecting the entire planet by using the stealth jet to fire the virus high enough into the atmosphere that it would expand into a wide cloud that would engulf the planet.
However Chris and his new partner, Sheva Alomar, working for the B.S.A.A. finds Wesker's lab and took on both him and the infected Jill Valentine. Wesker fights for a short while but then leaves Jill to finish the team off while he leaves to finish his plans. The B.S.A.A. team manages to survive as well as free Jill rom Wesker's control. Wesker fearing the two were too close, turns on his partner Excella and infects her with Uroboros, turning her into a massive B.O.W. This give Wesker enough time to finish stocking his plane and prepare for takeoff.
Chris and Sheva mangoes to defeat the fully mutated Excella and follows Wesker where they fight. However, Wesker gets cocky and catches a rocket in mid-air (dumb move dude). Chris manages to shoot it causing a tremendous amount of damage to Wesker. At this time Chris and Sheva double team him and inject him with the serum to overdose him, making him as weak as a normal human. Now weakened, Wesker flees into his jet taking off. Chris and Sheva manages to get onto the jet where they fight Wesker once again (timing is everything in this fight, if the player doesn't hit the button that appears on the screen in enough time, you're dead). The two manages to fight Wesker off and open the underside of the jet causing it to decompress and crash into a volcano.
Wesker along with Chris and Sheva manages to survive. Of course Wesker is now agitated so he infects himself with the Uroboros Virus which turns him into a monster. In his mutated state, he chases Sheva around the edge of the lava pool before fighting Chris and Sheva head on. The two manages to throw him into the molten lava, but Wesker still lives. As the two board he helicopter, Wesker flings a tentacle at the helicopter grabbing a hold of the bottom. With an attempt to pull the helicopter down into the volcano, Chris and Sheva shoots twin RPGs ending Weskers madness.
(Apparently this is the end for this character but don't quote me on that. I still have an inkling that Capcom will have Wesker pop back into the picture. Of course so far it looks like we won't be seeing another appearance by Albert Wesker.)