The unnamed individuals have been held prisoner for months or possibly years in the underground Project Valhalla bunker underneath the Cold Steel complex. The prisoners are subjugated to many tests and given dosages of Valkyr in the bunker, where the members of the project attempt to create a serum that gives its users enhanced abilities, without the mind-altering side effects. Though the prolonged exposure to the Valkyr doses caused the test subjects to develop superhuman stamina, they are also in a constant delusional, crazed state of mind; constantly muttering to themselves, shouting nonsensical sentences, or frantically screaming.
The imprisoned test subjects are all dressed in a uniform of green, loose-fitting clothing with short sleeves, but they have no shoes or socks, which leaves the subjects barefoot. In spite of the test subjects' lack of protection from bullets, they have a considerable amount of resistance to firearm damage, most likely due to their extensive Valkyr exposure, (which is similar to Jack Lupino's ability to withstand being shot many times without dying, as he seemed to be a heavy "V" user).
Depending on the amount of Valkyr in their system, the test subjects range from practically harmless to manic killers. When Max Payne discovers a computer in the Project Valhalla bunker where the test subjects are held and experimented on, he learns that the three test subjects were given double their usual dose of "V" and sent to the Payne Residence with guns under the guise of collecting data on how the test subjects behaved in an urban setting. Under the influence of so much Valkyr, as well as being armed and in an uncontrolled environment, the test subjects became extremely unstable and violent, tearing apart the house and killing its inhabitants. When Max arrives and confronts them, the test subjects seem unaware of where they are or who Max is, but in spite of their lack of awareness, they still shoot at him as they probably see the detective as a threat.
Aside from the test subjects that Max encounters in his home in 1998, the others that he comes across while in the underground Project Valhalla bunker are a lot more benign, simply muttering to themselves and act unconcerned over the imminent destruction of the facility and massacre of the project's scientists by the Killer Suits. When shot, the imprisoned test subjects seem to cower and not attack, which might suggest that the level of aggression that a Valkyr user displays depends on the amount of "V" that person has in their system.
It is unknown where the test subjects came from or who they were before becoming captured and experimented on by the members of Project Valhalla. The project was officially terminated by the U.S. Army in 1995, but Nicole Horne used her influence and money to keep the project open unofficially. For the next three years the experiments continued in the old Project Valhalla bunker, with the project's researchers continuing in their attempts to perfect the drug without the damaging side effects, which also meant that human trials continued with the test subjects.
Main article: Prologue (The American Dream)
Alfred Woden leaks sensitive documents regarding the continued existence of Project Valhalla to the District Attorney's office that Michelle Payne is employed at. Nicole Horne then finds out what happened and, in order to prevent any further leak of the documents, uses the test subjects as a way to eliminate Michelle and her family, under the guise of a "field test" on the subjects' behavior in an "urban environment" for Project Valhalla. Three test subjects are given guns, double their dosage of Valkyr, and then dropped off at the Payne Residence to be let loose on the house and its inhabitants.
The frenzied, manic test subjects murder Michelle and her baby, Rose. Michelle's husband, NYPD detective Max Payne, comes home to find it ransacked and hears his child and wife screaming and men shouting. A test subject confronts Max outside of his daughter's room and the delusional man begins firing at Max, but he is taken out by the detective; another test subject comes out from another room and begins shooting at Max as well, but he is also taken down after being shot several times. The third test subject is killed in Max and Michelle's bedroom, after Max finds him standing over his wife's body.
Main article: The Deep Six
Three years after the deaths of Michelle Payne and her daughter, Valkyr has become a popular new drug in New York City, being manufactured in the Project Valhalla bunker and channeled through the Punchinello Crime Family all the way to street-level dealers, creating a multi-faceted drug ring that makes finding the source of the drug almost impossible. When Max Payne finds the project's underground bunker, he learns that an order has been made to Nicole Horne's hired men, the Killer Suits, to kill everyone related to the project and destroy the evidence, which includes the bunker itself. Going through the facility to get the answers he needs, Max comes across the bodies of several test subjects, in addition to a few still trapped in their cells. After Max finds out about Project Valhalla and its connection to his wife, he escapes from the bunker before it self destructs, which effectively ends the production of Valkyr, the project, and the human test subjects.
- The Valkyr junkies found throughout the first game are comparable to the test subjects, such as their passive, delusional behavior and speech. The junkies also have a similar response as the test subjects when they are provoked, going into a frenzy of violence and that, coupled with their enhanced strength and stamina due to their Valkyr addiction, makes them formidable opponents.