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"The lesson will be taught in due time, Aloy. Until then, we wait."
This article contains heavy spoilers. Read ahead with caution.

GAIA is a hyper-powerful artificial intelligence that played a major role leading up to the events in Horizon Zero Dawn, and is a returning character in Horizon Forbidden West. The single most powerful, most advanced A.I. ever created capable of advanced planetary engineering, 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.


Following the Battle of the Alight, Aloy spent six months fruitlessly searching for backup copies of GAIA to no avail, as Ted Faro's deletion of APOLLO had purged the backup copies of GAIA along with it. However, Sylens learned through interrogating HADES that backups existed within the HADES Proving Lab, which was isolated from any external signals and therefore unaffected by Faro's purge. Aloy found two intact data modules within: while they only contained GAIA's root kernel and were devoid of any subordinate functions, Aloy was able to locate MINERVA, which it could use to reboot GAIA's heuristic matrix. At the same time, Far Zenith used their own Elisabet Sobeck clone, Beta, to take the other root kernel.

After restoring MINERVA to its original form, Aloy was able to awaken GAIA. Initially, the AI mistook her for her creator before accessing the data on her Focus and learned the truth. After granting access to the facility to Varl and Zo, GAIA showed them to the lab where Aloy could repair corrupted machine overrides while her heuristic matrix became fully functional.

GAIA next spoke with Aloy in regards to two major threats: the missing subordinate functions and Far Zenith. GAIA quickly ran a search for the former; while APOLLO, ARTEMIS and ELEUTHIA were missing, she was able to locate AETHER, DEMETER and POSEIDON in the Forbidden West, though HEPHAESTUS had hidden itself in the global Cauldron network. Aloy had to recover the subordinate functions so GAIA could gain enough strength to subdue HEPHAESTUS and through it, the entire terraforming system to ensure the stabilization of the biosphere. As for the strangers who stole the other GAIA backup, GAIA speculated they were descendants of the Odyssey's colonization of Sirius and that they were the ones who sent the Extinction Signal to awaken HADES.

GAIA then assigned Aloy to retrieve the three subordinate functions to grant her enough heuristic density to fully absorb HEPHEASTUS, otherwise the rogue machine crafting AI would absorb her instead. With HEPHAESTUS, she'd be able to retask the machines of the terraforming system to stabilize the biosphere, as well as manufacture an army to defeat the Zeniths. While Aloy was away collecting the subordinate functions, GAIA focused on training her allies in use of their Focuses and well as shared what information she knew of the world of the Old Ones.

After Aloy returned with the first subordinate function, GAIA informed her of an SOS signal from ELEUTHIA. She asked Aloy to investigate whether or not the signal was genuine and summoned Varl and Erend to assist her. It turned out the distress signal was from Beta, who had managed to escape the Zeniths and stole the other GAIA root kernel. Through Beta, it was revealed that Aloy and GAIA's initial assumption regarding the Zeniths was incorrect; the Zeniths were not descendants of the original Sirius colonists but rather a faction of Old Ones who had achieved physical immortality. With Aloy's encouragement, a pessimistic Beta began working with GAIA on a way to capture HEPHAESTUS.

When Aloy later returned with the second subordinate function, GAIA advised her to speak with Beta for information on Tilda van der Meer.

After Aloy had procured the third subordinate function, GAIA, along with Beta, laid out the plan to capture HEPHAESTUS: Beta would construct a rig with enough data storage to transport GAIA to Cauldron GEMINI, which her predecessor constructed with two data cores after it was damaged by seismic event. However, any attempt to merge with HEPHAESTUS would create a significant power surge the Zeniths would detect, so Aloy proposed having Erend, Zo and Kotallo spread out to the other Cauldrons and use pulse generators in an attempt to confuse the Zeniths. Even though GAIA calculated that such a tactic would be effective, Beta informed them that HEPHAESTUS had written Alpha Clearance out of its access module. Aloy then suggested they find Ted Faro's Omega clearance. Though Beta protested that it was located in Faro's private bunker, Thebes, and that the Zeniths only knew of its general location in San Francisco, fortuitously, Aloy was aware that the Quen had set up a base in the city and decided to seek out Alva.


Following Aloy's unsettling experience in Thebes, GAIA informed her that she estimated the merge with HEPHAESTUS would take 35 hours, increasing the risk of detection by the Zeniths. So Aloy proposed that both she and Beta perform the merge, which GAIA calculated would take 4.5 hours. After Aloy managed to convince Beta to go through with the plan.

GAIA's matrix was then transferred into the transport rig and mounted on a Charger on the way to GEMINI. Once installed on the first core, GAIA summoned HEPHAESTUS. While it managed to escape the second data core, GAIA managed to keep it from escaping the Cauldron. After Aloy managed to force it back into the core, she and Beta attempted the merge. Unfortunately, they were interrupted by the Zeniths, who weren't at all fooled by their ruse. While Tilda betrayed the other Zeniths and escaped with Aloy, Varl was killed by Erik Visser, resulting in both GAIA and Beta's capture.

Both of them were brought to the Zenith base, where Beta was forced to begin the time-consuming task of merging HEPHAESTUS with GAIA, who was left impotent in her rig. Additionally, GAIA was merged with APOLLO, ARTEMIS and ELEUTHIA. Fortunately, in Aloy's attack on the Zenith base, aided by Tilda, Kotallo and Alva destroyed the base's regulator, allowing Beta to inject HEPHAESTUS into base's printer matrix, allowing it to rapidly manufacture combat machines that overwhelmed the Zeniths and their Specters.

As Aloy freed Beta, they learned the truth of the Zeniths' plans from Tilda. As it turned out, Sirius was destroyed by Nemesis, an immense database of the minds of Far Zeniths that gained sentience, and had sent the Extinction Signal to deny its creators a safe harbor on Earth. In truth, the Zeniths didn't want GAIA to retake the Earth, but rather to terraform a new planet for themselves while Nemesis scoured Earth in futility. Tilda still desired to carry out that plan and attempted to abduct Aloy as a way of making up for leaving Elisabet to die a thousand years ago, which ultimately resulted in her death.

With the defeat of Far Zenith, GAIA was returned to the Base, where she began calculating new options to recapture HEPHAESTUS, which had escaped back into the Cauldron network.


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.



AI Characters