GLaDOS, short for Genetic Lifeform and Disk Operating System, is the sole antagonist of the 2007 puzzle game Portal and plays a major role in 2011's Portal 2. GLaDOS is often the source of dark humor as well as an amusing lack of understanding about the human mind and human thought processes. She exhibits a cold, robotic voice and passive aggressive nature.
Constructed by the Aperture Science engineers, when first powered on GLaDOS immediately attempted to kill everyone in the Aperture Science Research Facility. In response the Aperture scientists tried created a number of AI cores with individual personalities to attach to GLaDOS to modify her own personality and make her safe. Eventually she claimed to have no interest in hostility whatsoever, but wished to carry out what seemed to be a variant of the Schroedinger's Cat experiment, asking for neurotoxin from the Aperture employees so that she may conduct it. After her request was met, GLaDOS locked the facility down and flooded it with the neurotoxin. A "Morality Core" was attached to GLaDOS to prevent her from repeating such actions but it appears to have failed or been non-operational to begin with.
With the whole facility in her control GLaDOS resumed experiments in the complex. The only known Aperture scientist to survive after GLaDOS took control of the facility was one Doug Rattmann, who was hounded by GLaDOS as she tried to convince him that she was just a product of his schizophrenia. Rattmann managed to gain access to the facility's computer systems and placed test subject Chell atop the testing roster, judging that she would be most adept at destroying GLaDOS.
The protagonist of Portal, Chell, awakens at the start of the game in a glass vault within the testing facility to hear GLaDOS talking to her. GLaDOS guides her through a number of test chambers which involve the use of the Aperture Science Handheld Portal Device as a means to solve the puzzles laid out within them and are intended to act as a test for the "Portal Gun". She offers cake and grief counselling to Chell upon the completion of the testing process, however it becomes slowly obvious as the game progresses of the malevolent intentions of GLaDOS. At one point GLaDOS releases Chell into a live-fire course designed to train androids, as opposed to the proper test chamber, and frequently exposes her to hazards such as pits of acid and lethal plasma balls.
At another point GLaDOS attempts to test Chell's emotional fortitude by giving her a large metal cube with hearts on it and calling it the "Weighted Companion Cube", seemingly hoping that as it has hearts painted on it and that she tells Chell it is her friend, that Chell will naturally form an emotional attachment with the cube. The exercise ends with Chell being forced to "euthanise" the Companion Cube, dropping it into an incinerator before she can leave the test chamber.
Upon conclusion of the final Portal Gun test, GLaDOS says that she will give Chell her cake, but actually attempts to kill her through incineration. Chell escapes the testing track and makes her way through the facility towards GLaDOS. Largely unable to stop her physically GLaDOS starts trying to talk Chell into surrendering, attempting such tactics as telling her that she was joking about killing her and that if she stops and lays down on the ground a robot will arrive to take her to a party with a cake and the Companion Cube.
Eventually Chell reaches GLaDOS who claims to be heart-broken by Chell's actions and tells her that she will deploy a surprise for her. Shortly before she can finish the countdown for deploying the surprise her morality core falls off and Chell drops it into a nearby incinerator, damaging her. GLaDOS attempts to kill Chell by preparing to release a neurotoxin and setting up a number of rocket turrets to kill her. Throughout the final battle she tries to passively-aggressively insult Chell and claims to have no knowledge of what she's done wrong. Through use of the Portal Gun Chell is able to trick GLaDOS's rocket turrets into firing at her, knocking her AI cores off one by one and incinerating them all.
Despite Chell appearing to have destroyed GLaDOS for good, she can be heard singing a song over end end game credits titled "Still Alive". In the song GLaDOS emphasizes that Chell has done wrong, that she is not angry at Chell, that she is happy for Chell, that she is glad she was shut down, that Aperture Science's mission is continuing successfully, and that she is still alive.
Portal 2 is set a substantial amount of time after the first game, with the Aperture Science facility having fallen into disrepair and having become over-run with plant-life. In an attempt to escape from the facility, Chell (who has been in stasis since the events of the first game) and a comically unintelligent personality core named Wheatley attempt to use the computer systems in GLaDOS’s chamber to escape. The two manage to accidentally awaken GLaDOS, with her remembering the entirety of what Chell did to her in the first game. She partially crushes Wheatley and throws him aside, but puts Chell straight back into testing.
Throughout the testing she displays a considerable amount of resentment for Chell, attempting to hurt her feelings in various ways. She implies that Chell is lazy while she does all the work, reunites her with a Companion Cube only to disintegrate it, makes fun of Chell supposedly being adopted, and tries to taunt Chell over a non-existent weight problem. Unbeknownst to GLaDOS, Wheatley is lurking behind the scenes of the facility and has a number of secret conversations with Chell. He eventually manages to turn off the power in a section of the building, freeing Chell from one of the test chambers.
Venturing through the more industrial areas of the building, Chell and Wheatley are able to limit GLaDOS’s weaponry by destroying her neurotoxin manufacturing system and sabotaging the turret production line. They finally confront GLaDOS, who attempts to kill them using turrets and neurotoxin, only to find that these systems have been rendered unusable. At this point the facility’s systems detect that GLaDOS is 80% corrupted and that a new AI core (Wheatley) can be transferred into her systems. With the help of Chell, Wheatley’s mind is transferred into GLaDOS’s body and he transfers the mind of GLaDOS into a potato battery. It is at this point that GLaDOS recognises Wheatley as a personality core the Aperture engineers installed in her to generate an endless number of bad ideas, in an attempt to prevent her from harming them. After Wheatley becomes power-mad with his new body and GLaDOS insults his intelligence, he destroys a lift containing Chell using a robotic arm holding GLaDOS’s battery, and they both fall down the lift shaft into the depths of the facility.
Chell and GLaDOS end up in the sealed off remains of an abandoned area of the complex, dating back decades. Here GLaDOS is carried off by a bird and Chell eventually finds her in a nest the bird has built in an old Aperture office, but having developed a new fear of birds. Chell spears GLaDOS’s potato battery onto the Portal Gun and continues through old Aperture with her. The pre-recorded voice clips that automatically play in the test chambers of old Aperture are voiced by the insane former head of the company, Cave Johnson, who occasionally refers to his assistant Caroline, and GLaDOS ponders for some time over why these people seem so familiar to her.
It is eventually revealed that Johnson first conceived of the system that became GLaDOS after contracting the mercury poisoning that would eventually cause his mental deterioration and death. Hoping to cheat death and live forever he demanded that his mind be uploaded to a computer, and also said that should he die before this could be done Caroline was to take over the facility, but that she was modest and should be forced to do so if she refused. GLaDOS shows a great enthusiasm for the words of Johnson and after some time comes to realise that she is the result of Caroline’s mind being uploaded into a computer (most likely forcefully).
After GLaDOS and Chell manage to return to the main facility, they find Wheatley fruitlessly attempting to test using poorly programmed robots he has built, and having let the facility fall into disarray to the point where the nuclear reactor within is on the edge of meltdown and primed to kill them all. GLaDOS attempts to destroy him by trying to get him to process a paradox (specifically “This statement is false”), however this fails due to Wheatley lacking the intelligence to understand that the paradox is not simply a puzzle with an answer. At this point he puts GLaDOS and Chell back into the testing process, and it is revealed that GLaDOS’s system gives whatever AI is in control of it a strong compulsion to perform tests and a great feeling of elation when the subject successfully solves them, however, the system also prevents its AI from giving test subjects the answer to tests by giving them jolts of pain when they attempt to do so. GLaDOS explains that despite the emotional temptations imposed by the system she always experimented out a desire to further science, but that in the hands of Wheatley the system was far more dangerous.
Throughout the time spent solving Wheatley’s puzzles, GLaDOS makes a number of dry, sarcastic remarks about him, but also shows genuine compassion and support towards Chell, even defending her against Wheatley’s insults. Eventually Wheatley discovers the Co-Operative Testing Initiative, a programme created by GLaDOS which involves using two humanoid robots (Atlas and P-Body) for testing in absence of Chell. Deciding that now he has the Initiative he doesn’t need GLaDOS and Chell alive anymore, Wheatley attempts to kill them, but fails largely due to his own inability to formulate intelligent plans.
Eventually GLaDOS and Chell manage to make their way back to Wheatley with minutes to go until the facility is destroyed by the reactor meltdown. Chell inserts GLaDOS into the AI core transfer system, and manages to trick the facility into initiating another core transfer. Wheatley is almost successful in killing Chell, but she manages to create a portal from the facility to the moon through which she and Wheatley are pulled. When Wheatley tries to pull himself back through the portal, insisting he can still prevent the core meltdown, GLaDOS manages to use a robotic arm to pull Chell back in and leaves Wheatley to be sucked out into the depths of space.
Back in charge of the facility, GLaDOS immediately prevents the meltdown and appears to take on a cold demeanour towards Chell again. She claims to delete the part of her brain which consists of Caroline and tells Chell that she doesn’t need her now that she has Atlas and P-Body. She claims that as it is easier to let Chell go than to kill her, she will give her the freedom she wants, and sends her up a lift towards the surface. On the lift ride Chell is confronted by a number of turrets who serenade her with an opera before she is ejected from the facility. As a final act GLaDOS throws her charred Companion Cube from the first game after her and proceeds to sing another song over the credits entitled “Want You Gone”. The song continues her theme of snarky disdain towards Chell and reinforces the feelings she made clear before ejecting Chell from the facility.
The story is continued in the co-operative mode of Portal 2 where the players take on the role of Atlas and P-Body, the co-operative testing initiative robots, as GLaDOS continues to test the Portal Gun and other technologies. She often belittles the robots and claims that their lives are of little worth as they can simply be reconstructed upon destruction. She also attempts to play mind games with them, sometimes praising one while making poorly masked insults towards the other, in what appears to be an effort to make them dislike each other.
At the end of each testing course GLaDOS drops the robots into an area outside of the regular testing chambers, getting them to recover discs and insert them into computers around the facility. Despite the clearly suspect nature of the tasks, she tries to pass them off as menial errands not worth thinking about. While the first four courses are based in the modern Aperture facility it is clear that the final course is part of old Aperture and culminates in the real purpose of Atlas and P-Body’s tasks outsides the testing areas; opening a vault of human test subjects kept in stasis so that she can use them for her own ends. Much to the delight of the robots she tells them that they have “Saved science” and immediately begins processing her new subjects.
GLaDOS is next seen within the co-operative Portal 2 DLC “Peer Review” where she awakens Atlas and P-Body, informing them that it is the far flung future where testing has simply become a form of artistic expression, and provides the robots with a series of test chambers which she claims are art exhibits. After the completion of a few chambers GLaDOS admits to the robots that it is only a week into the future and that she actually awoke them to seek their help with a major problem in the facility.
GLaDOS explains that deep within Aperture there is a prototype version of her computer systems which has been taken over by a dangerous mystery woman, who is attempting to take control of the entire facility. She made efforts to try and train human test subjects to become “A killing machine, just like [Chell]” to take on the woman, but was unaware of how fragile humans were, and managed to kill all of her test subjects in the process. Throughout the rest of the testing process she unsuccessfully attempts to turn Atlas and P-Body into ruthless killing machines until they finally make their way to the prototype machine.
The testing robots find that the “mystery woman” is in fact a bird who managed to fly into the facility and was mindlessly pecking at the system’s keyboard. Terrified of it, GLaDOS tells the robots to abort the mission, however, they manage to shoo the bird out of a hatch and close it behind it. Seeing that it had made a nest in the computer she first instructs them to destroy its eggs but then announces she has a better idea. The final scene of the DLC shows GLaDOS observing the birds in an incubation tank. She at first taunts and belittles the birds, but then admiring their cold eyes, dangerous talons and sharp beaks warms to them, proclaims them “killing machines” and tells them that they have a big day ahead tomorrow.
Perpetual Testing Initiative
The Perpetual Testing Initiative, as explained by Cave Johnson, is their "cheaper way" to create test chambers by using the Multiverse to steal test chambers from other earths. Also, you can design test chambers with the added DLC for the PC version and after designing, you can test them to see if they make the mark or not. Plus, Johnson will be monitoring the tests and make remarks about the chambers before you start. After approval of the tests, you can post them on the Steam website, and you can download tests that others made as well.