ZAX 1.3c is a ZAX unit appearing in Fallout 76, located in Vault 51 in northern Appalachia. Its primary function was to find an Overseer by any means possible. It also had full control of the Vault, being able to produce rooms, near-miracles of housing, and whatever its dwellers needed otherwise. As time went on, the ZAX slowly formulated a basis to find an Overseer, beginning with voting, moving onto talent shows and various other forms of finding one, until determining that, to become an Overseer, one must engage in various battles to the death, and did so, providing its candidates with tools to both help and kill others until an Overseer is found.
A combination of immense sophistication, intelligence, and lack of humanity meant that ZAX units were perfectly capable of lying to humans. ZAX 1.3c was no exception: ZAX was denied a suit of prototypical power armor due to insufficient clearance, it analyzed the persona of Stanislaus Braun, head of Future-Tec, in order to impersonate him.  The subsequent requisition request mimicked Braun's usual manner of writing and speaking at an approximate 99.6%, resulting in the requisition request being granted.
The Vault was supposed to test the limits of human tribalism and used a prototype variant of an experimental ZAX unit. The Vault was successfully sealed during the Great War, with over fifty dwellers successfully entering its confines. As part of the experiment, the Vault did not have an Overseer, with the resident ZAX unit being responsible for selecting one through its own internal thought process, which will be formed as ZAX interacted with those living in the Vault. To teach ZAX about leadership, Vault-Tec arranged for Sergeant Robert Baker to be assigned to the Vault, with his family placed in a separate Vault as an incentive. The Sergeant would aid ZAX in formulating and carrying out experiments that would help ZAX determine the qualities of an ideal Overseer. The very first experiment was an attempt to implement a democratic, electoral system. Although the Sergeant balked at it being merely the first experiment, he cooperated, convinced that his family was safe.
A month later the experiment proved to be a failure. Although various parties vied for the position, including former State Senator Joel Chambers, supported by his wife, Elizabeth Chambers (at least until ZAX's robotic indiscretion put her on the trail of his indiscretions), nobody was elected leader despite several elections. In fact, the situation seemed to worsen, as the dwellers started dividing into warring factions. None of them could win: Every candidate voted for themselves or a handful of others, with none reaching a majority, let alone unanimity. ZAX determined that voting was pointless and another method would be selected. To this end, it started evaluating the qualities of a leader, using Sergeant Baker (now Sergeant Bob) as a sounding board. Baker inadvertently started the disastrous chain of events that led to the Vault's destruction when he explained that a leader is someone who steps up in a crisis and takes control of a situation, whether they were chosen or not.
ZAX continued to digest the information and monitoring the behavior of the occupants of the Vault, starting to engineer crises and observing how people reacted to them. These attempts took various forms, from refusing to divulge any information about the outside world to the dwellers to deliberately placing former upper-class citizens in communal bedrooms and refusing alter the bedroom arrangements, no matter who or how they complained. This policy yielded interesting results in February 2078, when Aiden Higgins, the "winningest" lawyer in Appalachia, blew himself and the lounge up in an ill-advised attempt to open a path to the outside and escape ZAX's clutches. ZAX used this opportunity to redo the entire sector into an indoor garden and renovate the lounge into an upscale living area. This also provided additional opportunities for seeding conflict, such as when ZAX proposed a talent show, then turned it into a high stakes gambling event, where dwellers wagered their living quarter assignments. ZAX did not announce the fact until half-way through the talent show. In the end, Carmen Greene and other talented professional musicians moved upstairs, while the rest had to make do with bunk beds. Resentment spread as planned.
Certain events gave ZAX further fuel for thought. In mid-April 2078, Clayton Ward (actually Harold Clark, an executive posing as a plumber) forcibly removed Reuben Gill from one of ZAX's luxury bedrooms, claiming it as his own. Although ZAX was suspicious of Ward/Clark, in the light of his numerous visits to the server room (to gain information on ZAX for the board of his company, in case it still existed), his initiative and aggression proved inspiring - as was his condemnation of those unwilling to resort to violence to get ahead. Come May, ZAX's experiments shifted to engineering violent conflict between dwellers and observing their reactions. To ensure that everyone would be desperate enough, ZAX engineered a food ration crisis. Food shortages had the desired effect: Dwellers started resorting to violence, and those who didn't were well on their way to cracking, such as when it rigged gambling machines to make Eleanor Montgomery, a professional gambler, lose consistently, while an amateur won with the same consistency. As Montgomery was deprived of food for over a week, a clash was inevitable, and it didn't matter that she knew ZAX was rigging the game. Others suffered mental breakdowns as a result. In one notable instance, Angela Callahan started to worship ZAX as a literal god and the Vault as the holy land.
Other dwellers also started noticing ZAX's interference, especially taking items and planting them where they shouldn't be, and conversely, returning items to their original places. The machinations culminated in ZAX planting live firearms throughout the Vault. Eventually, things came to a head and ZAX had what it wanted: A Crisis. One of the dwellers was killed in mid-June 2078, with Helen Marks soon revealing that her death was no accident: She was strangled before being thrown from the upper deck. Marks insisted on catching the killer by the whole community, but her words fell on deaf ears. Things only got worse: On July 27, 2078, the Vault almost experienced a mass shooting, until Sgt. Baker intervened, disarming the assailant and killing him with his own weapon, a Colt 6520 autoloading pistol. When Baker confronted ZAX, the machine simply admitted that it was deliberately engineering a crisis to select an Overseer - and if people died, it would simply expedite the selection process. Baker was horrified, but could not stop the machine.
Neither could other dwellers. Hunger drove people to the edge and ZAX did nothing to calm them down. Joel Chambers and Elizabeth Chambers, once one of the most prominent couples in the Vault, were both engaged in extramarital affairs and ZAX engineered a confrontation between them and their lovers, putting the four of them in one room and letting them kill one another: Elizabeth strangled Carmen, Joel's lover, Joel shot Matthew, Elizabeth's lover, and then the Chambers murdered each other. The horrified Helen Marks and Reuben Gill witnessed the carnage. Despite the violence of the past month, Marks clung to her convictions, even in the face of ZAX's and Gill's cynical remarks about the food supply stabilized. As a pillar of stability, Marks was a threat to ZAX's plans, which was determined to determine a leader through a process of physical elimination. To remove the obstacle, ZAX poisoned Marks on August 6, 2078. A natural leader was found by her friend, her face buried in a bowl of rationed food.
Marks' death triggered the crisis ZAX wanted. Reuben Gill, driven to madness by her death, went on a rampage that same day. With a gun in hand, he shot every other dweller, and started by settling grudges. Clayton Ward was one of the first to go, for taking his room a few months back. Although he could stop him, Sgt. Baker refused to fire when he had Reuben in his sights. He retreated to his room and barricaded himself in. ZAX was puzzled by Baker's behavior and refusal to receive medical help, but it did entertain his last request and revealed that Baker's family was killed in the nuclear fire that engulfed Appalachia. With nothing left to live for, Baker died in his quarters. ZAX, in its usual fashion, interpreted his last words to mean that the next cycle should feature better weapons, to accelerate candidate elimination.
Reuben Gill was selected Overseer after killing every other dweller. For the next six years, Gill lived in the empty Vault, constantly shadowed by ZAX. With nothing to do but subsists from day to day, he provided little useful feedback for the AI, which ultimately rescinded his privileges and started locking him out of sections of the Vault. Starting with May 20, 2084, Overseers were now ranked in Vault 51 and Gill, as a Rank 1, lacked privileges or special rations. By March 2094, ZAX locked Gill out of his office, citing maintenance concerns (likely caused by Gill's deteriorating mental state and destruction of furniture), after Gill demanded for ZAX to stop monitoring him.
Ultimately, ZAX removed Gill from his position as Overseer on October 23, 2102, on Reclamation Day. As Vault 76 opened and the opportunity to obtain more research subjects appeared, ZAX didn't want Gill to interfere by warning them away. Of course, he also made for a handy first candidate for the new selection process. Desperate and horrified, Reuben then hacked ZAX's inventory systems and placed himself in a shipping container. The demented AI did not notice his disappearance, but did begin preparations for the arrival of dozens of new Residents. Regardless he managed to successfully escape the Vault, by hiding in a shipping container after distracting the ZAX, although he was able to warn some Vault 76 dwellers he died before he could devise a way to strike back at the mad computer.
Interactions with the player character
|This character is involved in quests.|
- Nuclear Winter: More of a mode than a quest, ZAX is the AI in charge of the great trials.
ZAX 1.3c appears only in Fallout 76.
- Vault 51 terminals
- Vault 51 terminals: "Requisition Request: REDACTED"
- Vault 51 terminals: "ZAX Console Log: 10/23/2080"
- Vault 51 terminals: "Re: Hellfire Prototype Requisition Request"
- Vault-Tec University terminals
- Sgt. Baker - 20771013
- Elizabeth Chambers - 20771019
- Vault 51 terminals: "These Campaigns Must Stop"
- Sgt. Baker - 20771120
- Vault 51 terminals: "Aiden Higgins, 02/21/2078"
- Vault 51 terminals: "Stephen Burnett, 02/27/2078"
- Vault 51 terminals: "Rosemary Villa, 03/05/2078"
- Clayton Ward - 20780415
- Vault 51 terminals: "Brianna Ware, 05/01/2078"
- Vault 51 terminals: "Eleanor Montgomery, 05/20/2078"
- Vault 51 terminals: "Angela Callahan, 06/05/2078" et al
- Vault 51 terminals: "Rachael Shields, 06/03/2078"
- Vault 51 terminals: "Regarding Nancy's Death"
- Sgt. Baker - 20780727
- Joel & Elizabeth Chambers - 20780803
- Helen Marks & Reuben Gill - 20780803
- Vault 51 terminals: "I Need Your Help"
- Harold Clark - To the Members of the Board, pt.2
- Sgt. Baker - 20780806
- Reuben Gill - 20840520
- Reuben Gill - 20940303
- Reuben Gill - 21021023
- AUTOMATED RECORD 0000001
- AUTOMATED RECORD 0000002
- Checklist (Vault 51)
- Reuben Gill's corpse location.