"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.

Firebreak is an ancient ruin in Horizon Zero Dawn: The Frozen Wilds. It is located on a mountain in the Banuk region known as The Cut, in what used to be Yellowstone National Park. The mountain is known as Thunder’s Drum. The ruin is in fact the remains of the ancient facility that housed the 21st century project known as Firebreak.


Firebreak is located on a vast plateau on Thunder’s Drum. The front of the facility is an enormous, imposing wall, now encased in ice, with vents and a door. The door opens to a power plant known as the Battery Facility. This power plant is still operational, presumably kept online by the artificial intelligence CYAN. Beyond the power plant is another large area, which leads to yet another large area with a huge geothermal energy tap. The far end of this area allows access to rooms and offices overlooking a huge cavernous chamber with rivers of magma flowing among large plateaus of solid rock.

Firebreak’s colossal front wall.

Both aforementioned large areas are patrolled by Daemonic Machines deployed by the A.I. HEPHAESTUS; those in the second area are much more dangerous than the first. At the far end of the magma chamber is the door of the large research and development cauldron built at the very back of Firebreak by HEPHAESTUS, designated Cauldron EPSILON. Deep within EPSILON, next to the cauldron’s core, was Firebreak’s main control center, where it kept CYAN imprisoned.

In various parts of the facility including EPSILON, are Datapoints relating to Firebreak, its purpose and its personnel. Within EPSILON are two data nodes at which CYAN managed to leave distress messages explaining what became of the facility and directions on how to break HEPHAESTUS’ hold on it and free CYAN. These can be accessed by overriding.


The Faro Plague

Firebreak’s governing A.I. CYAN

Project Firebreak was a top secret 21st century project implemented to stabilize the Yellowstone supervolcano. Managed by the artificial intelligence CYAN, Firebreak was successfully implemented. However the coming of the Faro Plague required that the entire project be hidden from the robots to prevent its destruction. Thus CYAN was put into hibernation and the project was powered down to a level that allowed its energy signature to be masked by the area’s geothermal activity. Firebreak therefore remained undetected by the marauding robots, and CYAN came out of hibernation after the Plague had been shut down.

Discovery in the New World

By the time CYAN’s hibernation ended, the Faro Plague had long consumed all life on Earth, including Firebreak personnel. CYAN remained in total isolation for the next eight hundred years, while Zero Dawn reestablished life and human civilization reappeared. However, through no fault of Zero Dawn, the humans of the new world lived primitive, tribal existences, with absolutely no knowledge of pre-extinction technology. Thus when the Banuk shaman Ourea chanced upon Firebreak and CYAN, she believed that CYAN was a spirit. She formed a very strong friendship with the highly benevolent A.I. based on her need for a confidant and CYAN’s need for company after eight centuries of isolation.


Cauldron EPSILON’s door.

Sometime after Firebreak was discovered by Ourea, CYAN was seized and enslaved by HEPHAESTUS, a malevolent and far more powerful artificial intelligence. Formerly the Zero Dawn machine manufacture Subordinate Function, HEPHAESTUS used CYAN to gain control of Firebreak. It did so in order to site EPSILON there because of the unlimited geothermal energy available to power the cauldron, and the unlimited mineral resources available from the magma that Firebreak tapped into. When CYAN appealed to Ourea for aid, Ourea enlisted her brother Aratak, the chieftain of her werak. They led an expedition to Thunder’s Drum, but the expedition was routed by the Daemonic Machines that HEPHAESTUS deployed in the facility as guards. Moreover, breaching EPSILON’s door was impossible. Most of the party was killed.


The arrival of the Nora huntress Aloy brought a solution. She came to The Cut to investigate HEPHAESTUS and its possible responsibility for the augmented machines she had heard were in the region. She, Ourea and Aratak eventually mounted a second expedition to Thunder’s Drum against HEPHAESTUS. This time it ended successfully. They defeated or avoided the Daemonic Machines, Aloy used her Zero Dawn access privileges to open EPSILON’s door, and they made it to the core, freeing CYAN and destroying a unit of HEPHAESTUS’ new anti-human hunter-killer machine, the Fireclaw. CYAN initiated a chain reaction that destroyed EPSILON. However the success came at the cost of Ourea’s life. She willingly sacrificed her life to override the core, freeing CYAN.

Current Status

When Cauldron EPSILON was built and went online, a thick, ominous cloud crackling with red lightning could be seen continually spewing forth from the top of Thunder’s Drum, similar to a volcanic ash cloud. With EPSILON’s destruction, the cloud is no longer present.

CYAN is now housed at Firebreak’s auxiliary control center, known by the Banuk as Ourea's Retreat. At Firebreak itself, the battery facility remains operational, with the now open door in the front wall allowing access. Curious delvers can go though the facility; however they may have to contend with any Daemonic Machines that survived Aloy’s expedition. If they do so, they can proceed all the way to EPSILON’s door. However, not even Aloy can proceed any further than EPSILON’s door should she return to Firebreak; the cauldron’s destruction has permanently sealed the door.

Neither the Faro Plague nor the new world events that occurred in the facility have diminished Firebreak’s success in its purpose. To the contrary, CYAN spent her eight centuries of isolation optimizing the project. It predicts that the Yellowstone Caldera’s stability will be maintained for at least another 3,337 years.



Frozen Wilds Audio Datapoints

Frozen Wilds Text Datapoints - Quests


  • Nothing like Thunder's Drum actually exists in the real world. However, it is visually similar to Devils Peak in Wyoming, nearly 400 miles to the east.



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