"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.

"A Fortress that defended mankind from a terrible danger..."

"Here's to you, Kenny. You put a cork in the Yellowstone Caldera; I think you deserve a margarita."
Anita Sandoval to Kenny Chau, following Project Firebreak's completion

Project Firebreak was a top-secret environmental protection project designed to stabilize the Yellowstone Caldera beneath the mountains of what was once Wyoming in North America. It is overseen and maintained by an AI called CYAN. The ruins of its facility, now called Thunder's Drum by the local Banuk, serve as a location in Horizon Zero Dawn: The Frozen Wilds.



In the mid-21st century, the world was in turmoil. Catastrophic climate change had led to shortages of food, resources, and habitable land. Fortunately, the world came together in a series of actions known as "The Clawback," which involved incredible innovations in green robotics, terraforming technologies, and artificial intelligence. However, another immediate threat to all mankind lurked just under North America: the Yellowstone Caldera threatened to become unstable and wipe out much of the planet.

The solution came in the form of Project Firebreak. With Faro Automated Solutions' head Ted Faro providing funding and resources, and renowned scientist Elisabet Sobeck innovating the technology, the construction of a sprawling underground complex was begun. Utilizing special technologies, overseen and managed by the Caldera of Yellowstone Analytic Nexus (CYAN), the facility was designed to hold the volcanic activity in check. The facility was fully automated, so it would only require minimal human attention as it fell to CYAN to govern and optimize its functions.

The project proved to be very successful and was originally expected to prevent Yellowstone's eruption for at least 1,665 years. It also provided unlimited clean geothermal energy to the North American continent.

Following the project's completion, Yellowstone Park was closed to the public to keep Firebreak under wraps, leading to numerous conspiracy theories about activities in the park.[1]

The Faro Plague

In 2064, the Faro Plague, ironically caused by Ted Faro who had funded the entire Firebreak project, spelled doom for mankind. Project Zero Dawn was started, with Operation: Enduring Victory being implemented to buy time for the project. Zero Dawn would give humanity a second chance, but it was also up to Firebreak to prevent the world's upheaval in the meantime, so the facility was left running. At the behest of Anita Sandoval, the project's lead programmer, the project's director Kenny Chau put CYAN into hibernation and powered down the facility to mask its energy signature from the marauding robots in preparation for the inevitability of the Yellowstone area being overrun. These measures protected CYAN and the project from being discovered and destroyed. CYAN's final contact was with Chau, and after that Firebreak was left untouched for centuries.

New World

The AI HEPHAESTUS, formerly the GAIA subroutine responsible for designing the machines that Zero Dawn used to terraform the planet back to being able to sustain life, had judged the human species to be a threat due to human hunting of machines. Commandeering at least five of the Zero Dawn Cauldrons, it began to design machines firstly to discourage hunting via inducing fear of machines in the human population. When this failed, it graduated to developing machines to actively cull the human population. Discovering the existence of Firebreak, HEPHAESTUS saw an opportunity: unlimited energy, resources, and an entire facility to research, design and build its hunter-killer machines. Thus it sent a direct network connection request to CYAN. The benevolent AI, lonely after centuries of isolation, eagerly accepted, and the vastly more advanced and capable HEPHAESTUS overwhelmed and enslaved it, taking full control of the entire facility.

Contact with Ourea and Aloy

However, before encountering HEPHAESTUS, CYAN had formed a strong friendship with the Banuk Shaman Ourea, who encountered CYAN when she found herself in Firebreak's auxiliary control center while hiding from Carja raiders. Completely ignorant of the technology of the Old Ones, Ourea thought the AI to be a spirit of the Banuk tribe’s revered Blue Light. When CYAN appealed to her for aid after her capture, HEPHAESTUS cut off CYAN's contact between the two.

Sometime after, the Nora huntress Aloy heard tales of new and deadly machines attacking the Banuk tribe and came to investigate. Teaming up with Ourea and her brother, the Banuk chieftain Aratak, they entered the Firebreak facility and purged CYAN of HEPHAESTUS's control. Unfortunately, this came at the cost of Ourea's life and the facility was heavily damaged in the purge.

Current status

Firebreak, in spite of the heavy damage to the facility, remains active under the watch of CYAN, who managed to fine-tune and heavily optimize its functions during its centuries of isolation. It is estimated to prevent the Caldera's eruption for over 3,000 years to come.



  • Firebreak's name is based on a firefighting technique used to combat the spread of forest fires, by creating areas where all the potential fuel (trees, brush, deadwood) has already been removed or burned, essentially creating an invisible barrier where a fire cannot pass.


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