"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 late 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 Analysis Network (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. Efforts were taken by Anita Sandoval, the project's lead programmer, and Kenny Chau, the project director, to keep the facility hidden from the Swarm in the inevitable event that the Yellowstone area was overrun. CYAN's final contact was with Chau, and after that Firebreak was left untouched for over three centuries.

New World

One of GAIA's subroutines, the HEPHAESTUS AI, in charge of designing the machines that now inhabited the world alongside the reemerging humans, had judged humanity to be a threat and began to design machines to hunt and kill humanity. However, HEPHAESTUS was unable to gain full control of the Cauldron facilities it needed to create even more deadly machines. Happening across Firebreak, it saw an opportunity: unlimited energy, resources, and an entire facility to build whatever it wanted.

CYAN, deeply depressed and lonely, did not think twice when it received a request for a direct network connection, thinking it to have come from advanced human survivors. Before it realized the threat, the vastly more advanced and capable HEPHAESTUS overwhelmed and enslaved CYAN, taking full control of the entire facility. For four years, CYAN tried to resist but was met with ruthless punishment.

Contact with the Ourea and Aloy

One day while fleeing Carja soldiers during the Red Raids, the Banuk Shaman Ourea found herself in Firebreak's auxiliary control center where she met with CYAN for the first time and, largely ignorant to the technology of the Old Ones, thought the AI to be a spirit. HEPHAESTUS soon found out about CYAN's attempt to call for help and cut off contact between the two.

Sometime after, the Nora Brave 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, fortunately 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.


  1. Creatures of Terror
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