Mass Effect: Return from the Shadows
The quarians are a nomadic species of humanoid aliens known for their skills with technology and synthetic intelligence. Approximately three hundred years before the events of 2183, the quarians created the geth, a species of rudimentary artificial intelligences, to serve as an efficient source of manual labor. However, when the geth gradually became sentient, the quarians became terrified of possible consequences and tried to destroy their creations. The geth won the resulting war and forced their creators into exile.
However, near the end of the war with the Reapers, with the help of Shepard, a Geth named Legion, and the rest of his crew, the Quarians were able to reclaim their world, which they now share with the Geth.