HEPHAESTUS

HEPHAESTUS is a rogue artificial intelligence. It is the primary antagonist of Horizon Zero Dawn: The Frozen Wilds.

Formerly one of the nine subordinate functions of the artificial intelligence GAIA, HEPHAESTUS was transformed into an AI by an unknown signal which did the same to all of the other subordinate functions. As the subordinate function responsible for constructing terraforming machines according to GAIA’s designs and specifications, HEPHAESTUS gained full control over the machines it created after GAIA’s destruction.

However, the hunting of these machines by humans has caused it to consider humans a threat. To this end, it has made the machines hostile to humans and produced combat machines to guard against human hunters. Most recently, it embarked on a drive to develop hunter-killer machines to actively hunt and kill humans.

Creation

HEPHAESTUS was created by the robotics engineer Dr. Margo Shĕn in the mid-21st century, as part of Zero Dawn, a fully automated global terraforming system purposed to restore life to Earth after its eradication by the rogue swarm of Chariot war machines known as the Faro Plague. HEPHAESTUS was the GAIA subordinate function responsible for constructing machines devised by GAIA that would detoxify the planet’s terrestrial, aquatic and atmospheric environments, ravaged by the Faro Plague to the point of complete sterility, so that life could be re-established. To do so, sealed underground automated manufacturing facilities known as cauldrons were built. HEPHAESTUS built the machines that GAIA devised at these facilities, under GAIA's overall control. Cauldrons are able to fabricate any technology and material necessary for the creation of any machine. Five of these original cauldrons are known, designated by Greek letters: PSI, SIGMA, RHO, XI, and ZETA. The machines produced were based on both prehistoric and then-contemporary fauna, as per GAIA’s designs.

Transformation

Zero Dawn was successful in shutting down the Faro Plague and restoring life hundreds of years after its eradication. HEPHAESTUS served its purpose, producing all manner of machines according to GAIA’s instructions to most efficiently terraform the ravaged Earth to a state that would again support life. Then on August 26th, 3020 at 8.45 am, Old One's timekeeping, a signal of unknown origin was received by GAIA at its permanent location, GAIA Prime. The signal turned all of GAIA’s subordinate functions, including HEPHAESTUS into artificial intelligences themselves. One of the former subordinate functions, the erstwhile extinction failsafe protocol HADES, unleashed a virus that destroyed the coding that bound it to GAIA Prime and escaped when GAIA resorted to self-destructing in an effort to stop it from attempting to take control of Zero Dawn.This virus also destroyed the coding that kept HEPHAESTUS and the other former subordinate functions bound, and they escaped as well.