The Reapers allow organic life to develop, with the Citadel serving its purpose as a hub for the intergalactic species of the Milky Way galaxy, until they are ready to harvest it.

[4] Upon invading through the Citadel at the conclusion of every extinction cycle, the Reapers quickly deliver a decapitation strike to the major population centers and leaders of organic civilizations, crippling their ability to react.

The Reapers then isolate each star system by controlling the galaxy wide mass relay network and engaging a war of attrition with the remnants of galactic civilization, hunting down any survivors via records kept at the Citadel.

In dialogue with Commander Shepard, Sovereign states that they do not refer to themselves by the term "Reapers", but rather it is a name given to them by the Protheans, who lived in the cycle immediately preceding the current one.

The Catalyst eventually came to a conclusion that conflict is inevitable, and decided to achieve this by harvesting organic civilizations at their peak, shortly before they are responsible for their own downfalls, and absorbing their genetic material into new lifeforms that it can maintain and preserve forever.

[5][6] The Reaper's true origins as depicted in the Leviathan DLC inform their overarching design, with the implication that they are thinking creatures which have adopted patterns of living, organic beings as part of their construction.

[7] Lead writer of the first two games of the trilogy, Drew Karpyshyn, explained that within the series, the Reapers are intended to have both the roles of creator and destroyer at the same time, an idea that explores what a deity might be within a hard science universe like Mass Effect.

[10] In this level, Commander Shepard has been tasked with investigating the loss of contact with Cerberus scientists analyzing the Reaper's remains, which is adrift in space.

[11] Watts admitted that the art team struggled to finalize the creature's visual design based on Hudson's ideas; multiple concept drawings including one resembling a giant human fetus was considered but discarded for not being adequately threatening, and that last minute modifications to the final iteration were still necessary in order to fulfill the "level of creepiness" and combat requirements desired for the boss fight.

Other units like the pariah were cut from the main game, as their original ability to teleport around the battlefield were causing issues with the Mass Effect 3 physics engine.

[16] The Illusive Man was originally intended to be the final boss fight, with the character transforming into a Reaper creature much like Saren at the end of the first game.

Upon being revived by the anthropocentric paramilitary group Cerberus, Shepard joins forces with its leader, the Illusive Man, to recruit personnel in order to stop the Collectors.

Shepard boards a derelict Reaper and acquires its IFF, then launches an assault on the Collector base which is located beyond the Omega-4 relay, where the incomplete Reaper-Human Larva is destroyed.

Shepard reaches a Reaper transportation beam following an extended battle in London to enter the Citadel despite being gravely wounded by Harbinger.

Extended Cut expands upon the game's original endings with an additional choice to refuse the Catalyst, which inevitably results in a Reaper victory over the current cycle of organics.

[25] Evan Narcisse, also from Kotaku, considered the Reapers to be frightening antagonists as they are entities that felt like "un-life" and represent the continual malevolent erasure of sentient life forms.

[27] IGN staff enjoyed the encounter with a smaller Reaper ship towards the end of Mass Effect 3 as they were afforded the opportunity to equip the M-920 Cain superweapon.

[18] Tauriq Moosa from Polygon suggested that the idea of an all-consuming uncaring god stretches across BioWare's most popular franchises, including Mass Effect.

He observed that Shepard spent the entire trilogy preparing for war against god-like beings who "essentially, created existence", and compared the Reapers' cycle of destruction by design to "children with an ant farm and magnifying glass".

[38] A prominent fan mod for Grand Theft Auto V replaces the game's floating blimps with a detailed model of a Reaper capital ship.