Horizon: Zero Dawn has a rather complicated story told over the course of its 12 hour playthrough via audio recordings, cutscenes and dialogue sequences with NPCs. It’s easy to miss a lot of the core of the story if you don’t fish out some of the details. However, this article will cover the basics to give you a rundown of what happened and how the game ends.
Horizon: Zero Dawn starts with Aloy as a baby with her guardian Rost. Both of them have been outcast from the Nora tribe, a primitive but stable group. They live on the outskirts of the land where Rost trains Aloy so she can compete in a fake Hunger Games-style event called the Proving, which if she wins it will allow her to join a tribe and no longer be an outcast. Aloy manages to win the Proving and become a Seeker after everyone else in the Proving is killed via sabotage. She seeks to gain answers about the sabotage by tracking down a splinter cell group from a tribe called the Carja.
The 13th sun king ruler of the Carja had originally waged war with the other tribes, but the 14th ruler managed to kill the previous ruler and steer the Carja away from their raiding and slave-harboring ways. However, the war managed to take a toll on the other tribes, especially the Nora; they regressed to primitive ways of dealing with their tribesmen, banishing them as outcasts if they dared venture into parts of the land that are deemed cursed. Their superstition is also what led to them brandishing Aloy as an outcast when they found her as a baby at an ancient door.
Aloy makes her way to the city of Meridian to track down Olin, who was at the Proving before the sabotage occured. While in the city, Aloy discovers that Olin was hired to betray all those in the Proving when the leader of the splinter cell group, Helis, captured Olin’s family and held them hostage.
Aloy manages to track down Olin, who is among a group of cultists in a gorge filled with dangerous machines. Aloy defeats the machines, kills the cultists, confronts Olin, and saves Olin’s family. Aloy learns from Olin that the Shadow Carja are known as the Eclipse Cultists’ they’re led by Helis, the former champion of the 13th Carja king who was also known as the mad sun king.
Helis wants to restore the Carja to power and make them great again, similar to when they were under the mad sun king. He wants the Carja to go back to being a tribe of conquerors before the 14th king took control. He’s driven by grief and anguish after his wife died during childbirth. He was resolved to continue on after the 13th king allowed Helis’ family to be buried in the cave of the royals, cementing Helis’ position as the chosen under the king. To this end, Helis believes his goals can be accomplished by following the commands of a machine overlord named Hades, and that the Carja can be restored to glory. Hades is the one who gives Helis his commands through the Focus device, directing and chiding him in the way of restoring the ancient machines, starting with the Corruptors, also known as Scarabs.
It’s explained that the Corruptors, the ancient war machines, can corrupt other machines, turning the robosaurs into rabid, violent attackers. The Corruptors are like the foot soldiers for the more devastating machines known as the Deathbringers, giant mechs filled to the brim with devastating firepower.
The Eclipse cultists plan on using the Deathbringers to wipe out the other tribes and restore the Carja to their original prominence.
Aloy manages to discover that the Eclipse gained control of the Deathbringers through an old Faro Automated Solutions facility – a company that was responsible for making the robots and the Focus devices. Aloy manages to infiltrate an abandoned Faro facility where she learns that they were responsible for making AI networks responsible for automated manufacturing of machine forces. She learns how the Corruptors were part of a Peacekeeper line of machines, which were used to take control of other enemy robots on the battlefield.
Unfortunately, Ted Faro, the owner of the Faro Corporation, ran into a problem when the AI had a fault: it became rampant. Faro tried a last ditch effort to get the programmer to build in a backdoor to take back control of the machines known as the Hartz-Timor Swarm, but it was already too late and the machines had become autonomous both within and outside of the network.
It turned out that the Chariot Line of Hartz-Timor Swarm Peacekeepers went rogue and began self-replicating through a cauldron known as the Horus Titan. In order to keep functioning, however, the Peacekeepers began converting organic material into biomass fuel, this included grinding up organic matter (such as plants, animals and humans) and turning it into fuel.
In order to prevent the entire destruction of the Earth, Dr. Elisabet Sobeck came up with the “Zero Dawn” project as a final solution to stop the Peacekeepers.
Aloy tracks down one of the machine manufacturing stations known as Cauldron Sigma, which looks like a mix between something out of The Matrix and Terminator.
Aloy ventures to the different machine Cauldrons in order to override their cores, which enables her to take control of the machines. However, the Eclipse cultists are already far ahead in their plans to overthrow Meridian, the capital of the Carja.
Along the way Aloy is guided by an explorer named Sylens who had previously aided the Eclipse in acquiring their Focuses from the Faro facilities. Sylens ended up leaving the Eclipse once he discovered what they were up to.
In one of the Faro facilities that Aloy infiltrates, a hologram from the past features a General Herres, who explains that Project Zero Dawn was not a super weapons program and that life on Earth was going to cease to exist no matter what. Aloy finds a hologram of Elisabet’s Zero Dawn project and it’s true that it’s not meant to save mankind, it’s meant to rebuild the world.
Elisabet explains that Zero Dawn is a sentient terraforming AI protocol that designates how organic life will reconstitute the planet. The AI is called “Gaia”, a literal AI version of mother nature.
Gaia as an AI is designed to run the encryption process to stop the swarm, but it will take around 60 years. Gaia’s purpose thereafter is to take back control of the machines, build new machines to help terraform, and use the machines to clean up the Earth so that Gaia can then begin to use the machines to gestate and distribute the seeds of organic life to repopulate the Earth over the course of 350 years.
Gaia was aided in the endeavor by other sub-routines, such as Hephaestus, which helped shape the machines to not only be adequate in navigating terrain, but also aesthetically to replicate past animals, hence why the machines that were built after the Swarm were wiped out began looking like robosaurs instead of war machines.
After the Swarm destroyed the Earth and Gaia went online, the AI eventually cracked the encryption of the Swarm and broadcast the deactivation codes for the Swarm army. In order to keep Gaia in check, a Matthew McConaughey wannabe named Travis Tate explains in a holographic backup that they made a failsafe called Hades. Hades’ job was basically a kill-switch for Gaia, forcing the AI to reboot and try again if the bio reconstitution failed the first time.
After Aloy gets the data from Elisabet’s office she goes back to the All Mother’s mountain and enters into the Lyceum, the place where humans are genetically bred by AI automatons. Aloy learns that over time Hades had become infected with the same virus as the Swarm and began attempting to usurp Gaia and destroy all life again. Gaia attempted to thwart Hades’ attempt by blowing up the reactor, destroying her and the other subordinate AI. Before doing so, Gaia gestates one more embryo with the DNA of Elisabet Sobeck… an embryo that eventually becomes Aloy.
Gaia designed Aloy to access all the Faro facilities and rebuild the planet using Gaia Prime that only she could access. Aloy learns that she’s the only one who can destroy Hades and she’s the only one who can restore the planet and purge the corruption.
When she reaches Gaia Prime it turns out that the people who were being bred and released into the wild – as tribesmen – weren’t receiving knowledge because the education and history subordinate known as Apollo was destroyed by Ted Faro. Faro destroyed Apollo and all of human’s culture and history because he felt it was a disease that would only curse the innocents to come. Thus, when Gaia began releasing people from the Lyceum they were released without the archived knowledge held within Apollo, thus they were primitive and had to start from scratch.
Hades, however, offered humans an opportunity to gain knowledge. Sylens meets Aloy at Gaia Prime, revealing that during a scavenge he found a Focus device and used it to locate an old Horus Titan, which contained some of the AI code of Hades before Gaia purged the system by blowing the reactor. Hades had Sylens find and repair more Focus devices and used him to establish the Eclipse cult to work as a personal army; Hades pretended to be a god to the Eclipse to create civil war with the Carja as a cover so that Hades could gain control of a tower called the spire. After Hades acquired what it could from Sylens, it launched a kill order against him, forcing him to become a fugitive on the run, hence this is why Sylens begins helping Aloy.
Hades also sought to kill Aloy because she represented the only thing that could stop him from taking over the transmission spire and rebroadcasting the Swarm virus again. Hades intended to revive all the biomass mechs and replication cauldrons that were decommissioned during the extinction.
Hades manages to launch his assault against the Carja in Meridian, which is where the spire is located. He takes control of the broadcast tower, raising the ancient army of machines in the process.
However, Hades and his army of killer mechs are unable to defeat Aloy and she manages to overcome the corrupted Deathbringers, kill Helis and his men, and destroy the Hades master control unit. Once Hades is destroyed, Aloy activates Elisabet Sobeck’s virus purge and deactivates the evil machines while cleansing them of the Swarm virus.
The game ends with Aloy finding the body of Elisabet while an audio recording plays of Elisabet explaining that if she had a child, she would want her daughter to be strong and unstoppable and capable of healing the world.
In a post credit scene it’s revealed that Hades lives and is captured by Sylens, who begins to question the AI about its masters and who woke up the AI and why they wanted it to destroy Gaia.
TL;DR: A rich white guy builds killer robots that destroy the entire planet. A rich white woman builds the entirety of mother nature into a super AI that looks like a black woman cosplaying as the Statue of Liberty — all in an attempt to fix the rich white guy’s mistake. It sort of works, but the rich white guy’s killer robots come back and ruin the benevolent black mother nature AI. As a last ditch effort the mother nature AI creates a perfect being in Aloy based on the rich white woman’s DNA. Aloy is designed so that she’s the only one who can stop the corrupting robot virus, and restore the Earth to its former glory.