A variety of Synths seen on Earth. Synth is the term for a class of alien creatures turned into war machines, and one of the several species that make up the
Union organization. They are officially described as "self-replicating robots that evolve", "created or taken over by the Universal Union and enslaved during their conquests and wars." Most Synths seem to possess both organic and robotic characteristics, suggesting that they may be the cyborg derivatives of alien races that were previously enslaved by the Union and assimilated into its armed forces.
The Synths that currently occupy Earth have been modified to fit our planet. The occupation force is designed to be nearly autonomous from the rest of the Union - it is rumored that the Synths are assembled in some of the more secret factories of
City 17, while some claim they come from the Citadel itself.
Synth's intelligence has been the subject of much debate - they appear to be completely sentient, yet no Synth has ever be reported to have disobeyed an order. It is believed that cybernetic part of the Synth's brain is loaded with what is essentially malicious software - basically inserted training and brainwashing to make the machine completely docile. This, unfortunately for the Union, hampers their total intelligence and effectiveness - Synths tend to act more like animals in a pack than anything else.