Reaper

The Reapers are a highly-advanced machine race of synthetic-organic starships. The Reapers reside in dark space: the vast, mostly starless space between galaxies. They hibernate there, dormant for fifty thousand years at a time, before returning to the galaxy.

These giant machines are ancient; their true name is unknown. "Reapers" was a name bestowed by the Protheans, the previous galactic power fifty thousand years before, and the geth refer to them as the Old Machines. In the end, the Reapers spare little concern for whatever labels other races choose to call them, and merely claim that they have neither beginning nor end.

The Reapers are the original creators of the Citadel and the mass relay network. These massive constructs exist so that any intelligent life in the galaxy would eventually discover them and base their technology upon them – all part of a scheme to harvest the galaxy’s sentient life in a repeating cycle of purges that has continued relentlessly over countless millennia.

Design
A Reaper is essentially "billions of organic minds, uploaded and conjoined within immortal machine bodies."

In terms of physical design, Reapers bear superficial resemblance to a cuttlefish or squid, with a bulky semi-cylindrical body, a tapering plate over the rear and five tentacle-like "legs" or arms extending from its front end, in addition to six jointed legs extending from its body. The rear-most of the larger legs have crescent-shaped extensions. Collossal in size, Reapers are known to range from 160 meters to over 2 kilometers in length.

The core of any Reaper is constructed in the image of the species that was harvested to create it, while the exterior follows a standardized design that is most efficient for their purpose. When the Reaper fleet is revealed in dark space, they are shown to all share the same basic design, but with great diversity in limb number, shape and orientation, some with extended heads and others having multiple glowing lights. This may illustrate the variety of Reaper subtypes, as it is revealed during the Reaper invasion of the galaxy that several different varieties of Reaper exist.

While the outward appearance varies between subtypes, all of them retain features of their forebears the Leviathans, an ancient aquatic race that dominated the galaxy in ages past. The largest known Reaper ships essentially copied the Leviathan form while the smaller ones diverge to varying degrees.

Subtypes
There are several varieties of Reaper, which vary significantly in size, purpose and firepower.
 * Harbinger: The first Reaper ever created, Harbinger appears to be of a unique subtype; Alliance intelligence identifies it as being the largest Reaper in the armada, and its design differs notably from the Capital Ship subtype, having only four main legs and multiple glowing "eyes". Exactly how much more powerful it is than a normal Reaper capital ship is unknown.
 * Capital Ship: Also known as Sovereign-class, the two-kilometer-long Capital Ships are the most well-known Reaper subtype. Their main weapon is a spinal mounted "magnetohydrodynamic" cannon with a yield of 132 to 450 kilotons of TNT, which dwarfs the main gun of an Everest-class Alliance dreadnought. No known ship, not even a dreadnought, has been known to survive a hit from this weapon. Capital Ships are also armed with multiple cannons in their "tendrils" capable of shearing through most opposing vessels in a single hit, a point defense system (similar to the GARDIAN systems favored by organics) for anti-fighter and anti-projectile purposes, and are capable of unleashing swarms of Oculi drones to engage fighter-sized craft. They are extremely durable, capable of taking the continuous and simultaneous fire of four dreadnoughts before they start to lose their kinetic barriers.
 * Troop Transport: Troop Transports vary in length between 200 meters and one kilometer and are used to transport husks to unconquered worlds and bring victims to Reaper processing centers. They lack sentience and are remotely controlled by the Reapers.
 * Processor: Mobile centers for mass DNA harvesting. Like the Troop Transports, Processors lack sentience and are controlled remotely by the actual Reapers.
 * Destroyer: Destroyers are only 160 meters in height, but possess a formidable capacity for destruction despite their reduced stature, with their main gun easily capable of destroying cruisers in seconds. Unlike Capital Ships, they have four main legs, along with five jointed appendages encircling their "head". The frontal plates of a Destroyer can fold to the sides, exposing a powerful beam weapon. They are used to escort the capital ships, destroying smaller targets such as frigates. On the ground, they are capable of unfolding their legs and walking to support the husks, becoming extremely powerful heavy walkers. They are nigh-immune to ground vehicle fire and not at all fragile in space, but a cruiser is noted to be able to take out a Destroyer fairly quickly.

Indoctrination
Reapers and their technology have been observed to exert a disturbing influence on organic beings. This mental manipulation is known as indoctrination. Put simply, any organic being who is in close proximity to a Reaper or certain Reaper artifacts for too long comes to believe the Reapers are correct in their goals, and will do anything to serve them. Gradually, the mind is eroded until the individual becomes a mindless slave no longer capable of independent thought.

Reapers can control the rate of this process. Optimally, the subject is led to believe it is still acting on its own convictions. Indoctrination can drive people mad outright, and people deemed useful by the Reapers are given just enough free will to remain competent at their tasks.

This indoctrination is permanent, almost impossible to subvert, and is one of the most insidious weapons of the Reapers. Entire civilizations can be delivered into the Reapers' hands by the indoctrination of a few influential individuals. During the invasion of Earth, the Reapers broadcast messages inviting diplomats into their holds to negotiate, where they would then presumably be indoctrinated.

A Reaper's indoctrination field can remain active even if it's is largely disabled and incapable of action. A Cerberus science team was indoctrinated by being inside a Reaper that had otherwise been floating derelict for 37 million years, its only obvious activity being mass effect field generation.

Technology
Even without their indoctrinating influence, Reapers are immensely powerful warships and their technology is devastating. One armament common with the various subtypes is a powerful "magnetohydrodynamic" weapon which ejects a stream of molten metal at a fraction of the speed of light, capable of tearing through a cruiser in a single sustained burst. The gigantic spinal-mounted gun of capital-class Reapers is able to rip through the hulls of even the largest of dreadnought-class ships with ease, effortlessly penetrating their kinetic shields. Reaper defences include powerful shields that could block the projectiles of an entire fleet, along with an incredibly strong hull.

Though they are sentient machines, the Reapers have habitable interiors that can transport a crew, either to help spread their indoctrinated slaves or to allow these slaves to tend to them, probably both. Speculation in the Codex suggests that each individual Reaper has a massive element zero core which, coupled with the likely enormous quantities of energies at its disposal, allows it to generate the staggering mass effect field needed to land ships of their size on a planet.

However, the Reapers are not invincible. When the Reapers go into states of hibernation between cycles, they are vulnerable. By taking refuge in dark space, the Reapers ensure they will not be discovered by accident and destroyed while they wait for their vanguard to open the Citadel mass relay. A concentrated effort by the fleets of organic races could also destroy a Reaper even if it is at full power.

Reapers recognize each other through a complex Identify Friend/Foe system. Reaper interrogation signals do not simply look for a friendly transponder code, they look for a friendly intelligence. If other races attempted to steal the IFF for themselves, the IFF comes with a virus that can potentially disable any system it's hooked up on. The virus can be countered; one of the known ways is to set an unshackled artificial intelligence upon it.

Aside from their formidable firepower and indoctrination, Reapers are also capable of mustering up their own ground forces to attack their enemies: husks. Husks are aggressive, mindless drones, created from organic beings who are exposed to Reaper technology, such as dragon's teeth, resulting in their organic bodies being consumed by cybernetics. Husks are used as shock troops and swarm enemies in waves. Occasionally, to bolster husk defenses the Reapers will employ devices known as Barrier Engines that cocoon individual husks in a durable biotic barrier. For long-range offensives they usually outfit their husks with integral weaponry, although Reapers have been known to also manufacture handheld weapons like the Reaper Blackstar.

Because of the Reapers' technological superiority, the galaxy's factions actively studied or reverse-engineered what they could from them. Known products of such research include the Thanix cannon, the M-597 Ladon, and parts of EDI's AI.

History
Reapers had been known to exist for nearly a billion years, judging by findings from the Leviathan of Dis, an ancient Reaper corpse.

Before the Reapers came to be, the galaxy was under the thrall of a race known as Leviathans. They created an "Intelligence" to solve the problem of organics and synthetics killing each other. However, this Intelligence turned on them, slaughtering most of their kind and processing others into the very first true Reaper, Harbinger. Harbinger's form, that of the Leviathans themselves, became the template for subsequent Reapers harvested from the galaxy's races on cyclical purges over the next millions of years.

In order to speed up the time between harvests, the Reapers constructed the mass relay network and the Citadel to coordinate it. Engineered creatures called keepers were placed on the Citadel to maintain the station during their absence and to open it for them when they decide to invade.

Fifty thousand years before the current galactic era, the Reapers initiated a purge against the Protheans, the dominant spacefaring lifeforms at the time. The Protheans tried to resist like so many others before them, only to fail through the Reapers' physical and insidious might.

The Prothean Counterattack
Not all Protheans perished in the genocide: a cadre of elite scientists hidden on Ilos survived by bunkering down into stasis until the danger has passed. Upon waking, it took them decades of study to realize how their civilization fell to the Reapers, but this discovery gave them the key to breaking the cycle forever.

The Protheans developed a plan to forestall the impending Reaper attack for future generations of sapient, spacefaring species. This plan hinged on the fact that the keepers have independently evolved, and now only respond to signals from the Citadel itself. The Reaper vanguard signals the Citadel which in turn signals the keepers to open the station's own mass relay, ushering in the next Reaper invasion. However, the Prothean scientists used a reverse-engineered prototype mass relay—the Conduit—travelled to the Citadel, and altered the Citadel signal. The scientists succeeded, but could not do anything about their own population numbers, so they still died out along with the rest of their race.

The Vanguard
The first living Reaper to be witnessed by any living intelligent being after the Protheans became extinct was designated Sovereign by the organic races. It was a colossal dreadnought, several times the size of any known vessel – even dwarfing the massive asari flagship, Destiny Ascension. It was first discovered on the edges of geth space in the Perseus Veil by Edan Had'dah's survey teams and studied by Dr. Shu Qian. Saren Arterius, using the doctor's notes stolen sometime in 2165 CE, eventually found it for himself.

At first, it was presumed to be Saren's flagship by those who encountered it; Sovereign did act as transport for the rogue Spectre and his geth minions. However, it was later discovered by Commander Shepard that Sovereign and its brethren were actually the masterminds behind the Prothean genocide. It acted as the Reapers' vanguard and was intended to initiate the next harvest of the galaxy.

When Sovereign decided it was time to begin the cycle again, the keepers ignored the order. This greatly complicated matters for Sovereign. In order to unleash its brethren from dark space, it would have to find a way to manually activate the relay from inside the Citadel. While Reapers are undoubtedly beings of terrible power and ferocity, a single Reaper would not be able to survive the combined might of the assembled Citadel races in a direct assault. It needed to find an agent that would lead it to the Conduit. This agent was Saren, who became capable of comprehending the vision from the Prothean Beacon. With a fleet of geth ships, the Reaper launched an all-out assault on the Citadel, nearly devastating the entire fleet.

Fortunately, Saren was stopped by Commander Shepard and company, and Sovereign was destroyed by the Alliance Fleet, though this would only forestall them for a few years. Shepard knew the Reaper fleet, though dormant and hibernating, was still out in dark space and vowed to find some way to stop them.

The Reapers and the Collectors
After Commander Shepard defeated Saren and Sovereign, the Collectors began attacking human colonies and abducting their populations. Cerberus determined that the Reapers were behind this and planned to have Shepard thwart this latest Reaper threat to humanity. Over time, Shepard uncovered disturbing facts regarding the nature of the Reaper connection to the Collectors. Apparently, because humanity is a race of great genetic diversity and was the race who defeated Sovereign, it was enough to gather the Reapers' attention. It is also revealed that the Collectors were originally Protheans who were captured by the Reapers and genetically repurposed to suit their needs.

The Collectors were working under the direct supervision of the Reaper Harbinger, who ordered the Collectors to abduct humans in the Terminus Systems. The captured humans were taken to the Collector Base and processed into organic matter to construct a new Reaper modeled on the human form. EDI speculated that this was the Reaper equivalent of reproduction. When discovered by Shepard, the incomplete Human-Reaper was composed of facsimiles of the skull, arms and ribcage of a human with its lower spine and torso still under construction. EDI concluded that tens of thousands of humans had already been processed. Shepard was able to stop the process and destroy the Human-Reaper.

With the Human-Reaper destroyed and the Collectors defeated, the Reapers lost any chance of using the Citadel mass relay to quickly return to the Milky Way galaxy. Harbinger and the rest of the Reapers, who have already been on the move since the destruction of Sovereign, are shown approaching the Milky Way, setting the stage for the Reaper War.

Arrival
As the Reaper fleet draws closer towards the galaxy, Dr. Amanda Kenson was exposed to a Reaper artifact showing her visions of the Reapers' plan: to enter the galaxy using the mass relay in the Bahak System, which sits at the edge of the galaxy. In order to delay their arrival, Kenson decides to destroy the relay by ramming an asteroid into it. However, before the plan could go to effect, Kenson and her team became indoctrinated by the artifact and she and a small team were then later captured by batarians.

This course of events would prompt Admiral Hackett to send Commander Shepard (or Alliance assets) to rescue Dr. Kenson and see what she was up to. This resulted in the destruction of the Alpha Relay and a further delay to the Reaper invasion, but at the cost of three hundred thousand batarians living on Aratoht.

Return to the Galaxy
Six months after the destruction of the Alpha Relay, the Reapers finally returned from dark space and began their next galaxy-wide harvest of advanced organic civilizations. Their invasion started in the Vular system in batarian space and rapidly spread along the mass relay network. Within days, the Batarian Hegemony was destroyed, Earth has fallen, and the Systems Alliance Navy was in full retreat, and a massive offensive was launched against the Turian Hierarchy. Over the following weeks, the galaxy's population centers were conquered or annihilated one by one as the Reapers inexorably advance. On Earth, the Reapers destroyed satellites and defunct nuclear missile silos. They soon began broadcasting orders, inviting human leaders into their superstructures to "negotiate peace." This was a ruse to indoctrinate them and pacify the population.

Commander Shepard, who had escaped Earth in the Normandy SR-2, began to actively work to unify the galaxy against the Reapers. The first step was attempting to secure a krogan-turian alliance by curing the genophage. Shepard managed to destroy a Reaper Destroyer attempting to use the Shroud tower on Tuchanka to poison its atmosphere by luring Kalros, the mother of all thresher maws, to it.

Further into the war, the Reapers became involved in the geth-quarian conflict. After the quarians began assaulting the geth in a bid to reclaim their homeworld, the geth sought the aid of the Reapers, receiving upgrades and greater fighting ability at the cost of their free will. Shepard managed to defeat the Destroyer broadcasting the control signal via heavy bombardment from the Migrant Fleet, freeing the geth from Reaper control. As it lay dying, the Reaper addressed Shepard and stated that the cycle of extinction must continue, although it did not clarify further before deactivating. Isolated pockets of geth mobile platforms still continue to serve the Reapers however, their programs having been replaced entirely with Reaper codes instead, though only making up a small fragment of the overall geth forces no longer under their command.

Despite the victory on Rannoch, the Reapers invaded the asari homeworld, Thessia. The asari, who had been performing hit-and-run attacks against the Reapers, were forced on the defensive as the machines gradually overwhelmed them.

The Reapers also became aware of Cerberus's attempts to find a way to control them. Henry Lawson ran a refugee camp called Sanctuary on Horizon to study indoctrination. Eventually, he learned that the Reapers use a signal to control their husks and found a way to co-opt it. However, while trying to find a way to apply this technique to the Reapers themselves, he underestimated the signal's strength, alerting the Reapers to his activities. In response, the Reapers assaulted Sanctuary.

Leviathan
While the Reapers carried out their latest harvest, they also hunted an old foe: the Leviathans. Although most Leviathans had been harvested to create Harbinger, some had survived and gone into hiding. The Reapers followed Dr. Garret Bryson's search for the entity that killed the Leviathan of Dis and sent forces after Bryson's researchers.

Commander Shepard tracked the Leviathans to 2181 Despoina, discovering the Reapers' beginnings from them. The Reapers also learned their forebears' location and a Sovereign-class ship showed up to investigate. Unfortunately for the Reapers, Shepard convinced the Leviathans to aid in the galaxy's fight. The Leviathans disabled the capital ship above their planet and permitted the galaxy's militaries to deploy their "artifacts" among Reaper troops, allowing the Leviathans to turn some Reapers against each other.

Crucible and Catalyst
During the war, the united forces were focused on constructing a massive superweapon, dubbed the Crucible, that could theoretically destroy the Reapers. The Protheans had attempted to build the weapon 50,000 years prior, but had failed. It was discovered by the scientists building the Crucible that, like the Protheans before them, they were missing a critical component called the Catalyst.

A Prothean VI named Vendetta revealed that the Catalyst is in fact the Citadel. The Illusive Man, having captured the VI, in turn revealed this to the Reapers. They responded accordingly by seizing the station and placing it in orbit of Earth. With little choice, the allied fleet engaged the Reapers while ground teams attempted to reach a conduit beam the Reapers used to transport living and dead humans to the Citadel in London. Unfortunately, the Reapers realized their intentions: Harbinger personally descended to Earth and sent the resistance forces into retreat. Only Shepard and David Anderson made it through to the beam.

The Reapers had anticipated this eventuality. The Illusive Man, who had "upgraded" himself with Reaper implants, had traveled to the Citadel before Shepard and Anderson. He immobilized them using his newfound abilities, failing to realize that he himself was indoctrinated. After Shepard killed the Illusive Man or convinced him to commit suicide, the Crucible was allowed to dock with the Citadel, where it would then determine the fate of galactic civilization and the Reapers themselves.

Purpose
Shepard soon after discovered the Catalyst, an artificial intelligence which embodies the Reapers' collective consciousnesses and memories, also known as the Leviathans' "Intelligence". Shortly after the Illusive Man's death, this entity took Shepard up to a part of the Citadel where no organic had ever been before, and began disclosing the Reapers' secrets. The Catalyst revealed that the Reapers came into being long ago when the Leviathans conceived it to seek a solution to the inevitable struggle between organics and synthetics. However, it decided that the Leviathans too risked conflict with synthetics and, using an army of "pawns", forcibly processed them into Harbinger. Despite this betrayal, the surviving Leviathans do not believe the Catalyst was a "mistake" and believe the Catalyst's use of the Reapers is part of an experiment on a galactic scale to seek a truly permanent method of preserving life.

For millions of years, the Reapers existed for the sole purpose of ensuring the ongoing existence of organic life in the galaxy, based on the assumption that all synthetic intelligences will eventually destroy their organic creators. This end result is believed by the Catalyst and the Reapers to be inevitable, a consequence of technological advancement; organics will always create synthetics to improve their own state of existence, and synthetics themselves will evolve by means of surpassing their creators. Indeed, available evidence seems to point to the validity of their assertions: the Protheans' civilization was threatened by synthetic uprisings before the Reapers wiped them out, and the geth of modern times are viewed as a substantial threat to peace in the galaxy.

By harvesting technologically advanced species (both organic and synthetic) and storing these old species within immortal Reaper bodies, room is made for new life to flourish and grow, as was the case for primitive man. The continuity of life in the galaxy is assured through this cycle of extinction, as it ensures that organic life will never be fully exterminated before its time by synthetic life, as was demonstrated by the quarians and the geth.

Fate
During the Battle for Earth, depending on Shepard's decisions and the level of galactic readiness achieved, the Catalyst gives Shepard up to three options:
 * Destroy the Reapers (Red) - Shepard will shoot and destroy a power conduit, causing the Crucible to unleash an energy pulse which will destroy the Reapers, the geth, and all other forms of synthetic intelligence in the galaxy;
 * Control the Reapers (Blue) - Shepard's consciousness will be transferred into the Crucible, destroying Shepard's physical body but gaining control over the Reapers;
 * Synthesis (Green) - Shepard will leap into the Crucible's energy beam, and the Crucible will emit an energy pulse that converts all life in the galaxy on the molecular level, causing all organic life to have partially synthetic traits and vice versa.

If Shepard chooses to destroy the Reapers, the Reapers will shut down and collapse and Husks will be obliterated. If the level of galactic readiness is below a certain level, the Crucible will be damaged on approach and misfire, causing the energy wave to kill indiscriminately. If the level of galactic readiness is high enough, however, the Crucible fires properly and Shepard manages to possibly survive the event. With the Reapers destroyed, the galaxy begins the long process of rebuilding and restoring the mass relays and Citadel.

If Shepard chooses to control the Reapers, the Spectre's consciousness replaces the Catalyst's AI and becomes a being with absolute control over the Reapers. They cease attacking, and Shepard directs them to restore the mass relays and help rebuild the galaxy. The Reapers become a supreme military force that guards the galaxy from anything that could harm its people.

If Shepard chooses to merge organic and synthetic life, the process obliterates the Commander but transforms all organics and synthetics across the galaxy into hybrid beings; organics would gain perfection through technology while synthetics gain understanding of organics. With the fundamental differences between organic and synthetic effectively erased, the Reapers cease attacking. They help rebuild the galaxy of their own accord, and share the collective knowledge of countless alien cultures that had come before.

Alternatively, Shepard can refuse the Catalyst's options, claiming that such a decision is unacceptable. The Crucible deactivates, and the Reapers go on to complete their purge of the galaxy, continuing the cycle for at least one more iteration. An untold number of years later, an unknown adult female and child are speaking of the archives that were stored in one of Liara T'Soni's time capsules. It is implied that through the use of this information, a future generation was able to halt the cycle and finally achieve peace.

The Cycle of Extinction
Vendetta explains on Thessia that the patterns concerning the development of galactic civilization and the cycles of extinction are too regular and repetitive to be coincidence. According to the VI, the galaxy experiences the same paths and conflicts during each cycle - "the same peaks of evolution, the same valleys of dissolution" - expressed in different forms. It infers that the Reapers are servants of this pattern, not the creators of it. The Reapers' true master and motive, however, remained largely unknown until Commander Shepard's meeting with the Catalyst itself.

The Reapers leave no evidence of their conquest, nor of their existence – only desolate, barren ruins of those who came before. Extant information on them is so scant that they are known merely as "boogeymen" at best in many cultures' ancient legends.

The trap created by the Reapers was simple. A sentient species would develop an FTL drive, but would still be limited in its speed. By leaving a network of relays capable of instant transport across the galaxy that led to the impressive Citadel, the Reapers ensured that it would become the center of galactic civilization. Further, Sovereign implies that the presence of the mass relays would lead the sentient species down a predetermined route with regards to weapons and armor technology (both of which are based upon element zero technology for the Citadel races). As Sovereign explains, "By using it [mass relay technology] your society develops along the paths we desire." The relays also serve to reduce the amount of time it takes for galactic civilization to advance, thus shortening the time between the Reapers' harvests.

Once the sentient races have established themselves on the Citadel with the aid of the keepers, a lone Reaper vanguard stationed within the galaxy sends a signal to the Citadel, instructing the keepers to activate the station’s hidden mass relay. This opens a path between the Citadel and dark space. The Reapers then flood through, killing the leaders of the assembled species before branching out and harvesting all spacefaring life around them.

Because the Reapers first enter the galaxy at the point that they have ensured will be the center of galactic politics, information and finance, they are able to cripple any resistance almost before the Citadel civilizations have any idea that they are under attack. The Citadel also gives them control of the relay network, cutting off star systems from each other and destroying communications.

The Reapers then use their control of the Citadel and its data to begin the most sinister phase of their attack. Records allow them to track down every settled planet and attack them, harvesting their populations or enslaving them through indoctrination.

Once they have harvested the galaxy, the Reapers wipe every trace of their existence from record and retreat back into dark space.

Harvesting
During their invasion at the end of each cycle, the Reapers gather and "process" vast numbers of individuals from each of the galaxy's sentient spacefaring races. Victims who cooperate with or are captured by Reaper husks are rounded up into "camps", where the husks select individuals deemed fit for processing; it is believed that the husks use scent or chemical receptors to analyze the genetic composition of victims. Those who are deemed unsuitable are turned into more husks. Individuals who are determined to be suitable for processing are loaded onto Reaper Processors, where they are ushered into single-person pods. Like a slaughterhouse, the interior of the Processor is designed to prevent any visual or auditory contact between individuals being processed. Once in the pods, the victims are dissolved into a raw genetic "paste" for ease of transport. This paste will then be used in the construction of a newborn Reaper, with the victims' minds being preserved to form the Reaper's gestalt consciousness. The only known facilities used for Reaper construction are located on the Citadel and within the Collector Base in the galactic core. Available information suggests that a single race is harvested during each cycle to produce Reaper Capital Ships; it appears that other space-faring races harvested during the cycle are used to produce Destroyer-class Reapers. Exactly how or why this distinction is made is unknown. The rate of killing during a harvest is staggering - during the invasion of Earth, at least 400 Processors were present, and the number of humans processed each day was estimated at 1.86 million. At such a rate, the entire planet would be depopulated in a decade. As a "back up" option, the Reapers are capable of using the Collectors - a slave race genetically engineered from the Protheans - to gather genetic material in their stead. The Reapers are only known to have used this option once, when they used the Collectors to conduct mass raids on human colonies as part of a plan to create a human-based Reaper.

Notable Reapers

 * Derelict Reaper
 * Harbinger
 * Human-Reaper
 * Leviathan of Dis
 * Sovereign

Trivia

 * The idea of a terrifying and incomprehensible alien intelligence waiting in the depths of space is a feature of Lovecraftian horror. This similarity is emphasized by one of the recordings by the survey team aboard the derelict Reaper which spoke of how "even dead gods can dream." This is a clear homage to Cthulhu, as "In his house at R'lyeh dead Cthulhu waits dreaming."
 * Another link between the Reapers and Lovecraft's work is his philosophy on Cosmicism. The Reapers are portrayed as incomprehensible with reasoning and long-term goals that are made out to be impossible for organics to ever understand. They also claim to be the pinnacle of existence and that organic beings could never obtain this level of meaning on their own.
 * The codex entry for Earth mentions that "Reaper gunships" are capable of "megaton-level firepower". This would give these gunships much more firepower than even Reaper capital ships. It is not known what these craft are, if the entry referred to a known Reaper subtype like a Destroyer, or if it was simply an error.
 * Dialogue was removed from Mass Effect 2 that details the Reaper harvesting process. EDI states that the captive humans were being reduced to their basic components by being dissected down to the atomic level. The data from the process could then be uploaded into a Reaper's neural network, thus storing the knowledge and essence of the individual that was liquefied in the process. Harbinger indicates that being turned into a Reaper is a form of rebirth. In reference to the fight with the Human-Reaper, Harbinger also states that Shepard is the one "wasting lives."