Reapers

Sentient starships that harvest the galaxy every fifty thousand years.

The Reapers are a fleet of sentient starships and the main antagonists of the Mass Effect trilogy. Inspired by the deities of H. P. Lovecraft's Cthulhu Mythos, they are cosmic horrors that cause galaxy-wide mass extinctions every fifty thousand years. Notable Reapers include Sovereign and Harbinger.

Quick Facts

Series: Mass Effect
Creator: Drew Karpyshyn
First major: Mass Effect (2007)
Last major: Mass Effect 3 (2012)
Leader: Harbinger

Facts from the source article.

Background

The Reapers hibernate in dark space, the mostly starless space between galaxies. They set up the Citadel, which is in fact a giant mass relay, and let organic life develop around it until they are ready to harvest. When they invade through the Citadel, they strike the major population centres and leaders first, then isolate each star system by controlling the relay network. They can brainwash organics through indoctrination and subvert synthetics with a galaxy-wide "Reaper code". The Leviathan DLC reveals their origin: the Leviathans created an AI, the Catalyst, to preserve organic life, and it turned its own creators into the first Reapers.

Lead writer Drew Karpyshyn said the Reapers were meant to be both creator and destroyer, exploring what a deity might be in a hard-science setting. Their look resembles the Ur-Quan Kohr-Ah of Star Control II. The Reapers regularly feature on lists of the greatest video game antagonists.

Sovereign is revealed as a Reaper in Mass Effect and is destroyed at the Citadel. In Mass Effect 2, Harbinger directs the Collectors, and the final boss is a human-form Reaper made from harvested DNA. In Mass Effect 3 the Reapers invade and overwhelm Earth, and the Catalyst offers Shepard the choice of how to use the Crucible against them.