Harbinger: The main antagonist of Mass Effect 2 and Mass Effect 3 (besides Illusive Man as the secondary antagonist), and leader of the Reaper fleet. It is the largest and oldest Reaper in existence and was the controlling force behind the "Collectors"; who were warped versions of the Protheans.

The Reapers are a fictional fleet of sentient starships that serve as the main antagonists of the Mass Effect trilogy. The design of the Reapers was inspired by H. P. Lovecraft's Cthulhu Mythos deities. Within the series, the Reapers cause galactic-level mass extinctions every fifty-thousand years.

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.

The Intelligence's betrayal of its creators was sudden and devastating. Its pawns slaughtered most of the Leviathans, using their genetic material to create the very first Reaper, Harbinger, who was physically designed after the Leviathans themselves.