GAIA

GAIA is the main A.I. overseeing Project Zero Dawn. A personification of Mother Earth, GAIA and her subordinate functions are tasked with re-terraforming the Earth back to its Pre-Faro Plague state.

Background
The product of Project Zero Dawn, GAIA is the main Artificial Intelligence charged with overseeing the re-terraforming and reseeding of life on Earth after its destruction at the hands of the Faro Swarm. GAIA was located at the massive underground facility known as GAIA Prime, which housed its computer core and other subordinate functions needed to ensure proper management of the re-terraforming process.

She stayed largely in contact with Elisabet Sobeck, to the point that they became good friends, with GAIA declaring that she knew Elisabet all too well. However, Ted Faro feared that should the AI become corrupted there must be a fail-safe. Elisabet did not approve, but GAIA accepted its practicality as an emergency course of action.

History
Sometime after GAIA was activated, the Alphas evacuated to GAIA Prime. She eventually made them aware of a malfunction in the security door that could make the swarm aware of them. With GAIA's help, Elisabet sacrificed herself for their safety. Soon after, Ted Faro contacted the GAIA Prime team with an urgent message. Using his security clearance, Ted Faro purged the APOLLO education and historical archive system, wiping out thousands of years of history and consigning future generations of humanity to ignorance and primitive lifestyles. Faro then went even further, and commanded the facility to vent its oxygen supplies, killing all of GAIA Prime's personnel.

Despite this move, GAIA maintained her role in not only deactivating the Faro Swarm but also bringing life back to the planet. She made the majority of her machines to regenerate life and detoxify the planet, and ordered Cradle facilities to begin repopulating the planet, but understood that without the knowledge of APOLLO the population would not learn to communicate with her. She also saw that the humans had become primitive compared to the late 21st century.

Unknown Transmission
In the 31st Century, GAIA received a transmission from an unknown source. This transmission had the immediate effect of causing all subordinate functions to become self-aware and erratic. One of the sub-functions, HADES, attempted to seize control of the terraforming system to destroy humanity. Unwilling to let this happen, GAIA activated a fail-safe, in which the reactor of the GAIA Prime facility was commanded to self-destruct in the hopes of destroying HADES. A second fail-safe was activated by ordering a gestation chamber in a Cradle facility to create a clone of Elisabet Sobeck. This clone, upon reaching physical maturity, would be able to use her DNA to enter all Project Zero Dawn facilities in hopes of rebuilding GAIA.

However, HADES reacted by unleashing a more powerful virus and destroyed the code holding it in place, allowing the AI to escape and corrupting some of GAIA's data, including the [Alpha Registry]] - the DNA security-system that would have allowed Elisabet's clone to enter the Cradle and view her message.

Trivia

 * GAIA is based on the Greek primordial deity Gaia who is the personification of Earth and the ancestral mother of all life. In Greek mythology, Gaia is the ancestor of all Greek deities. Similarly, she is the grandmother or great-grandmother of all named sub-routines contained within her AI.
 * Sylens states that it may in fact be possible to rebuild GAIA by using the Cauldrons' foundries to make the necessary parts; however, this could take years, and in any case the effort would be for naught until HADES is stopped and prevented from interfering.
 * The death of GAIA had many unexpected consequences:
 * Without a central governing system, the machines soon began to become deranged and attack humans without warning.
 * Without an extended backup to stop any subordinates from becoming self-aware, HADES attempted to wipe out any trace of the work GAIA had achieved.