Geth

History

The Quarians created the geth around the late 1850's CE to be used as laborers and tools of war. The quarians kept their programming as limited as that of any VI, nothing close to an AI, remaining mindful of the Citadel Council's laws against the creation of artificial intelligences. But as the quarians gradually modified the geth to perform more complex tasks, the geth developed a sophisticated neural network connecting them all together. This change altered the geth to such an extent that they became sapient, transforming into full-blown AI's ----- albeit with no sense of conventional individuality, as they operated as a permanently connected hive-mind and made decisions via consensus established by FTL communications between every member of the species.

As the geth began exploring the boundaries of their new-found intelligence, the quarians found it harder and harder to control them. One day, a geth unit asked its master "Does this unit have a soul?". According to Legion, this was not the first time a sapient geth had asked that question, but it was the first time that the question was met with fear.

Panicked, the quarian government ordered the immediate termination of all geth in the hopes of preventing a revolution. Many quarians did not want to oppose the geth, but were forced to give up or terminate their geth servants. After the quarian government declared martial law on Rannoch, those who sympathized with the geth were outnumbered, and an indeterminate number of them were either detained or killed. The quarian sympathizers have since been forgotten by their own people, though they are remembered by the geth themselves.

The quarians severely underestimated the power and sophistication of the geth's neural network. The geth reacted to defend themselves, and the resulting confrontation erupted into a planetwide war. Billions of quarians died, and the survivors were eventually driven from their homeworld. The only reason some quarians were able to escape was because after they had fled to a certain distance, the geth no longer recognized them as a threat and ceased pursuit. Legion lends an additional view to this when he says the geth were uneasy about the prospect of their first act as a free people being the annihilation of an entire species ---- let alone their own creators.

After the war, the quarian race lived among the Migrant Fleet ---- a fifty thousand strong fleet of starships that is home to about 17 million quarians, all that remains of their people. Meanwhile, back on Rannoch the geth adopted a policy of isolationism, preferring to keep to their own devices. As a mark of their regret over all the lives lost in the war, they maintained the abandoned quarian homes and buildings long after the quarians themselves were gone.

Mass Effect

The geth attack the human colony of Eden Prime, led by rogue Spectre Saren Arterius. It later transpires that the geth are helping Saren brign about the return of the Reapers, which they worship as gods. The geth follow Sarens orders without question, believing him to be the Reaper's herald due to him piloting the ship Sovereign (which is a Reaper itself).

Mass Effect 2

A docile geth dubbed Legion is encountered. It reveals that the geth that followed Saren were a small percentage of the geth collective, dubbed 'heretics' by the main geth who refused Soverign's offer to join it. In Legion's own words, the heretics want the Reapers to give them the future, while the main geth wish to build their own future.

Mass Effect 3

If Shepard allows the geth to achieve true intelligence, they will provide assistance to the War Effort. The Systems Alliance and the Turian Hierarchy receive geth support with open arms, although there is still some animosity between them.

If peace was made with the quarians, it is revealed that the geth are able to coexist with them on Rannoch. The synthetics help with setting up housing, with some even uploading into quarian suits, rewriting environmental functions. The intent is to mimic infections that, in time, will help the quarians to boost their immune systems, allowing the Creators to live without their suits.

If Shepard chooses to use the Crucible to destroy the Reapers, all synthetic life in the galaxy including the geth will be destroyed. If Shepard uses the Crucible to take control of the Reapers or merge all synthetic and organic life, the geth will help rebuild Rannoch. If both quarians and geth were spared from their mutual destruction and Shepard merged organic and synthetic life, the two races will be seen side by side. If both quarians and geth were obliterated during the course of events a desolate Rannoch dotted with ruins of geth structures is seen, the only legacy of two once-great races.