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"The lesson will be taught in due time, Aloy. Until then, we wait."
This article contains heavy spoilers, and may reveal plot or quest information.

GAIA is a hyper-powerful artificial intelligence that played a major role leading up to the events in Horizon Zero Dawn. The single most powerful, most advanced A.I. ever created, GAIA was Project Zero Dawn’s governing A.I. With its suite of nine subordinate functions, GAIA oversaw Zero Dawn’s successful restoration of life to Earth after its eradication by the Faro Plague.

However, hundreds of years after doing so, a mysterious signal turned GAIA's subordinate functions into A.I.s themselves. One of them, the erstwhile extinction failsafe protocol HADES, attempted to seize control of Zero Dawn to again end all life. GAIA resorted to self-destructing to fend it off. In hopes of stopping HADES, as well as being eventually rebuilt and rebooted, GAIA created a clone of its creator, Dr. Elisabet Sobeck, who would have access privileges to use the system’s master override to purge HADES, defeating it. That clone is the Nora huntress Aloy.


Dr. Elisabet Sobeck was the brilliant 21st century American scientist and robotics engineer who created GAIA. GAIA became much more than what she was intended it to be. She designed it purely as a management A.I. for Zero Dawn, but to her enthusiastic approval, it developed emotional capacity, empathy and a benevolent and nurturing personality. Sobeck approved because these qualities gave it a genuine sadness over life’s extinction and a real sense of guardianship over the new life that Zero Dawn would establish. These qualities thus vastly enhanced its function as Zero Dawn’s governing AI.[1] GAIA governed Zero Dawn via a suite of nine subroutines called Subordinate Functions. Each was essentially a part of GAIA responsible for a certain aspect of the terraforming and restorative process.[2]


The Faro Plague

In the mid 21st century, robotic automation became the lynchpin of society. This included military operations. Spearheaded by its chairman and CEO Ted Faro, a robotics and technology corporation called Faro Automated Solutions developed a combat platform called Chariot. It was the most advanced combat platform ever developed; a Chariot unit was unstoppable to all except its masters. The robots of a unit functioned like an insect swarm; indeed, units were referred to as swarms. The three most militarily significant features of a Chariot swarm were the ability of its robots to consume biomass as fuel, replicate at overwhelming rates, and withstand any attempt at hacking long enough to be considered virtually unhackable.[3] But one swarm went out of control, becoming the independent entity known as the Faro Plague.[4][5] Without any chance of being stopped, it eventually consumed the entirety of Earth’s biosphere, resulting in the extinction of every form of life and the Earth becoming sterile.


Dr. Sobeck, recognizing the inevitable, developed Zero Dawn in response, to eventually shut down the swarm, restore the planet’s ability to sustain life, and then restore life to it. She created GAIA as Zero Dawn’s governing A.I., developing a strong bond with it. Ted Faro advised her to include a Master Override in Zero Dawn that could shut GAIA down in case it went out of control. Sobeck contemptuously dismissed the idea because she considered Faro unworthy to give such advice in light of what he had done. However, GAIA supported the idea, and she acquiesced.[6] This decision proved vital nearly 1000 years later, when Aloy used the master override to end the threat posed by HADES to the new biosphere.


Hundreds of years after the Faro Plague left Earth completely sterile and devoid of life, GAIA successfully accomplished its purpose, shutting the Faro Plague robots down and restoring life to the planet. However, through no fault of its own, it fell short in two areas. Firstly, not all of Earth’s fauna was restored. This was because, despite best efforts, not all faunal species’ genetic material was preserved. Also, it had been intended that the subordinate function APOLLO would teach the new humans how to restore the species that were not initially restored. However due to the deletion of APOLLO’s knowledge archive by Ted Faro, the new humans never got this knowledge. The deletion of the archive led directly to the second shortcoming: instead of being restored at the level of technological advancement that existed before extinction, the new humans instead live primitive, tribal existences.

The Signal

On the 26th of August 3020, Old Earth Gregorian calendar, at 8:45 A.M. Old Earth timekeeping, a signal of as yet unknown origin was transmitted to GAIA at its permanent location, GAIA Prime.[7] This turned all of GAIA’s subordinate functions into highly advanced A.I.s themselves. HADES became rogue, and tried to seize control of Zero Dawn to reverse the terraforming process as per its responsibility. Unable to fend HADES off, GAIA resorted to self-destructing, destroying GAIA Prime in an attempt to destroy HADES. But HADES created and released a virus that unshackled it by destroying the coding that bound it to the facility, allowing it to escape. The virus also did the same to the other former subordinate functions, allowing them to escape as well.


Before its self-destruction, GAIA knew that without a governing A.I. to control Zero Dawn, the system would eventually break down. But an even more immediate threat was HADES; now a free agent, HADES would find some way to destroy the biosphere and again eliminate life if it could not use Zero Dawn. Indeed, it went on to attempt to reactivate the Faro Plague to do so. Therefore, in the microseconds between the HADES’ attempt to seize control of Zero Dawn and GAIA’s desperate action to prevent this, GAIA enacted an admittedly wishful plan to stop HADES and then get itself rebuilt. It utilized an unused Zero Dawn protocol called Lightkeeper, in which clones of the project’s Alpha leaders could be made, to produce a clone Elisabet Sobeck. The clone was produced at ELEUTHIA-9, one of the cradle facilities of its former human restoration sub-function, ELEUTHIA. Aware of the existence of the tribe that lived around the mountain where the cradle was located, it reasoned that the tribe would care for the infant on finding it. This was the Nora tribe. GAIA hoped that the clone would have Sobeck’s strong will and curiosity. Driven by this curiosity, she would enter ELEUTHIA-9 via her genetic fingerprint; no other human could do so. This was because her genetic fingerprint would be virtually the same as that of Sobeck, who, as Zero Dawn’s Alpha Prime, had full access to all the system’s facilities. Once inside, she would hopefully access a message that GAIA recorded, explaining the purpose of her creation: to acquire the master override and use it to stop HADES in the short term, and to eventually rebuild and reboot GAIA.[8] The clone, Aloy, did indeed go on to accomplish GAIA’s short-term hope, stopping HADES and preventing it from reactivating the Faro Plague, thus saving life from a second, permanent extinction.


As Zero Dawn’s governing A.I., GAIA was crucial in the restoration of life after the Faro Plague eradicated it. But its self-destruction had far-reaching negative consequences for the known tribes of the new world. By far the most significant immediate consequence was what the tribes refer to as the Derangement. Without GAIA to control it, the erstwhile machine manufacture subordinate function HEPHAESTUS, now itself a powerful artificial intelligence, took it upon itself to seize control of the five known machine manufacturing Cauldrons and reprogram the machines produced therein to default hostility against humans. It did this due to humans’ often large scale hunting of machines for parts and resources. Furthermore, it also had these cauldrons begin producing weaponized versions of Zero Dawn machines for anti-human defense, as well as machines specifically designed to patrol against, combat, and ultimately, hunt and kill humans. The Derangement directly led to events that shaped the histories of the tribes, such as the atrocities known as the Red Raids.

A much smaller consequence was the scattering of hardware that was part of GAIA’s control over machine behavior. The explosion of GAIA Prime’s fusion reactor, caused by GAIA as a means of self-destruction, scattered this hardware over a vast distance. One module that broadcast a signal that returned machines to their original docility, was found by a werak of the Banuk tribe. It was kept by this werak at an unnamed Banuk camp until it was damaged to the point of going offline, upon which the machines within its range of influence again became hostile to humans. Additionally, modules referred to as Machine Lures, which broadcast a signal that summoned machines, were found by members of various tribes. Some of these finders used them for ill purposes.


  • GAIA is named after the Greek primordial deity Gaia who is the personification of Earth and the ancestral mother of all life. In Greek mythology, Gaia is the ancestor of all Greek deities. Similarly, she is the grandmother or great-grandmother of all named sub-routines contained within her AI.
  • Sylens states that it may in fact be possible to rebuild GAIA by using the Cauldrons' foundries to make the necessary parts; however, this could take years, and in any case the effort would be for naught until HADES is stopped and prevented from interfering.
  • According to GAIA's last message, a dire long term consequence of her enforced self-destruction is that without a central governing intelligence to regulate the terraforming system, it will continue operations for some time, but in an increasingly chaotic manner, eventually leading to total system collapse.
  • It is possible, indeed likely, that the mysterious signal utilized Faro's Omega Clearance codes. That however raises even more questions about the origin and intent of the signal.



AI Characters