The Collectors are an enigmatic race that live beyond the Omega 4 Relay, a mass relay within the same system as Omega, in the Terminus Systems. They are rarely seen in Terminus itself, let alone Citadel space, and are generally regarded as a myth by Citadel citizens. Definite sightings of Collectors have been made on Omega every few centuries.
They are most well known for their odd trade requests for which they offer new technologies, often of a startling level of advancement. Their requests usually involve the trade of living beings in odd numbers and varieties, such as two dozen left-handed salarians, sixteen sets of batarian twins, a krogan born of parents from feuding clans, or two dozen "pure" quarians — quarians that have never left the Migrant Fleet due to illness, importance to the fleet, or disability. One of their current interests is in healthy human biotics. No one knows what happens to the individuals concerned after the exchange is completed.