Aloy challenges Aratak, but daemonic machines ambush them in the final stretch of the challenge. They team up to fight off the machines, and impressed by Aloy's skills, Aratak concedes leadership to her. Aloy, Ourea, and Aratak head for Thunder's Drum. They infiltrate the Old World facility built inside the mountain where Aloy discovers that the Spirit is actually CYAN (Laurel Lefkow), an AI designed to prevent the Yellowstone Caldera from erupting. Traveling further inside, they discover that the Daemon has already overtaken much of the facility, but CYAN suggests using lava from the caldera to destroy the infected areas while preserving the facility. It is also revealed that the Daemon is in fact HEPHAESTUS (Stefan Ashton Frank), another of GAIA's subsystems that manufactures machines. The group fights through HEPHAESTUS' defenses and Ourea sacrifices herself to override CYAN's core, allowing it to transfer to an auxiliary data center and initiate destruction of the facility. Aloy and Aratak escape narrowly. Aloy returns to the Banuk Shrine, where CYAN has transferred herself to, and CYAN provides additional information about the Old World but warns that HEPHAESTUS is still active somewhere, and will continue to build machines designed specifically to kill humans, which is why it tried to seize control of CYAN and its facilities. Aratak thanks Aloy for all of the help she has provided to the Banuk, and Aloy puts him back in charge of his people before parting ways.