The Collectors are the main antagonistic force of Mass Effect 2. A mysterious insectoid race hailing from beyond the Omega 4 Relay, they are responsible for abducting entire human colonies in the Terminus Systems, though the purpose for doing so is unknown.
The Collectors hail from beyond the Omega 4 Relay, and are the only species to be able to move freely back and forth through it: no ship that has passed through this Mass Relay has ever returned.
They occasionally enter the Terminus Systems and trade their technology in exchange for living beings in odd numbers or varieties (e.g. tow dozen left handed Salarians, sixteen sets of Batarian twins etc.).
Once the deal is complete they immediately retreat back into the Omega 4 Relay as quickly as they arrived. It is revealed in Mass Effect 2 that the Collectors are genetically modified Protheans, the race that fell victim to the Reapers in the previous cycle. They have been re-purposed by Harbinger to collect humans for harvest, with the ultimate goal being the creation of a Human-Reaper. After Shepard assaults the Collector Base and destroys the incomplete Human Reaper, he prepares to destroy the base, but the Illusive Man suggests that Shepard instead use a radiation pulse to wipe out all the collectors on board while leaving the technology intact for Cerberus to salvage and use against the Reapers. Whatever choice Shepard makes, Harbinger realises that the Collectors have failed in their mission and abandons them to their fate.
The Collectors return as DLC for Mass Effect 3's Multiplayer mode. A large amount of them had joined with the Reapers in hiding in Dark Space, and rejoin them in invading the galaxy in 2186. However, the Leviathan's manage to sever the Reaper's control over Collector's on the battlefield; while most of them die as a result, a small few regain their sentience and join the rest of the galaxy in the war, hoping the avenge the Prothean race.
The Collectors themselves are rarely seen since they usually operate through agents, such as the quarian Golo, to make their deals. It has been speculated that the Collectors make these strange requests because of strange fetishes or gruesome culinary tastes, but it is more likely that they perform genetic experiments on these subjects, possibly testing their viability for use in the creation of a Reaper. Regardless of the possible danger, their requests are often granted by fringe groups because the technology the Collectors offer in return is often extremely valuable, giving any race who receives it an immediate advantage before it becomes adapted to the galactic community. The Collectors are controlled by a single leader who can possess any member of its species at any time, instantly turning them into the most dangerous Collector on the battlefield. When a Collector is possessed by the leader the outer surface of their body appears to crack open, revealing an orange glow that resembles molten rock.
Upon studying the Collectors, Mordin Solus surmised that the Collectors are in fact mindless drones, "closer to husks than slaves" and lacking any form of culture. He observed that the Collectors show no concern for self-preservation, and will die in battle even if their fight is completely pointless. Believing that culture is impossible without intelligence, he hypothesized that the Collector living areas and bases are completely without any kind of art or creativity. All Collector technology and constructions, he said, exist only for their utility without ergonomics taken into account.
- The Collectors were originally inspired by electron microscope photographs of insect heads.
- In Mass Effect: Paragon Lost, several Collector Drones seen on the Collector Ship are two or three times larger than normal Collector Drones seen earlier in the movie, and in the games.