The Collector Base is a massive space station located in the galactic core on the accretion disk of a black hole. Home to countless Collectors, Seeker Swarms, and Collector-controlled Husks, Abominations and Scions, it also houses the Collector General, who is directly controlled by the Reaper Harbinger. The base can only be reached via the Omega 4 Relay and is surrounded by the Tartarus Debris Field—a vast debris field made up of the wrecks of ill-fated ships who tried to access the relay. Within the debris field, several Oculi hide, waiting to ambush intruding vessels.
The Collector Base presumably survives proximity to a black hole due to what Commander Shepard posits is Reaper technology, and keeps at least one Collector Cruiser docked with it, which is dwarfed in size by the base itself. The base has the same semi-organic interior as the Collector Cruiser.
Mass Effect 2
Suicide MissionCommander Shepard's goal throughout Mass Effect 2 is to locate the Collectors' "homeworld" and put a stop to their attacks on human colonies. After infiltrating and escaping a Collector Cruiser, the Collector homeworld is pinpointed near the galaxy's core. In order to safely cross the Omega 4 Relay, Shepard then locates a Reaper IFF. Once the suicide mission commences, the Normandy SR-2 arrives at the other side of the Omega 4 Relay, the Tartarus Debris Field. The Collector homeworld is revealed to be a large space station orbiting on the edge of a black hole.
After surviving a sudden attack by the Collectors' security systems, the Normandy destroys the Collector Cruiser sent to intercept it, and crash-lands on the Collector Base itself. Deciding that the base must be destroyed to end the Collector threat, Shepard divides the squad into several teams to enter the base and overcome its defenses: Collector troops, husks, and seeker swarms. After fighting their way deep into the base, Shepard and company locate the kidnapped Normandy crew, stored alongside thousands of other humans in pods. They discover that the Collectors are breaking down the human victims into an organic "paste," which is being piped off to another part of the base.
At the base's core, Shepard finds a Human-Reaper larva, constructed using thousands of abducted humans. The nascent Reaper is seemingly destroyed when Shepard shatters the feeding tubes that support it, causing it to fall into the depths of the base.
The Base's Fate
Safe for the moment, Shepard opens a terminal to re-program the base's systems to overload. As Shepard orders the team holding back the Collectors at the door to return to the Normandy, a message comes in from the Illusive Man. He asks Shepard to set the reactor to emit a radiation pulse instead of overloading it. This way, instead of the station being destroyed, the Collectors in the base would be killed and the technology left intact for Cerberus to use against the Reapers.
Depending on Shepard's response, certain squadmates will react. Should the Paragon response be chosen then Garrus, Legion, Zaeed, Grunt, and Mordin will speak in favor of preserving the base, reminding Shepard that it's just data and that destroying it serves no purpose. If the Renegade response is chosen then Tali, Kasumi, Thane, Jacob, and Jack will disapprove strongly, reminding Shepard of the sick experiments, while Samara and Miranda will have more neutral responses. If the neutral response is chosen then no squadmates will comment.
In the end, Shepard makes the decision and sets the reactor. However, the Human-Reaper climbs out of the pit and engages Shepard and the two squad mates. After the Human-Reaper larva is destroyed once and for all, Shepard hurries back to the Normandy with Seeker swarms and Collectors on their pursuit. The Normandy races away from the base as the countdown reaches zero, just before Harbinger vows to continue on its plans, and finally ends with the Collectors' destruction.
Depending on Shepard's choice at the end of Mass Effect 2, the Collector Base is either preserved for Cerberus or destroyed. If Shepard died during the mission, the star behind the Illusive Man will appear red and blue as normal; otherwise, the star is pure blue if Shepard destroyed the base or deep red if the Commander chose to preserve the base. Squad members will also comment on the decision after, showing agreement or disagreement depending on the choice made and each individual in part.
Mass Effect 3
After Shepard dealt with the Collectors, Cerberus sent teams through the Omega-4 Relay to salvage Reaper technology from the Collector Base, whether it was destroyed or preserved. In Cronos Station, it is discovered that Cerberus recovered the Human-Reaper and are using it to augment the station's functionality—either its brain if the Collector Base was preserved or its heart if the Collector Base was destroyed. When the Alliance captures Cronos Station, the Human-Reaper's remains are incorporated into the Crucible, becoming War Assets.
- The black hole and debris field are seen on the title screen of all versions of Mass Effect 2.