Harbinger

Harbinger is the main villain of Mass Effect 2 and one of the main villains in Mass Effect 3 (besides the Illusive Man). He is a Reaper, like Sovereign from the first game, and is the controlling force behind the evil aliens known as the Collectors. He directly controls the Collector General, and during gameplay he can possess the body of any regular Collector, changing it from a normal grunt into a powerful superpowered enemy with a damage absorbing barrier, enhanced durability, and the ability to fire biotic attacks and fireballs. Harbinger also expresses an interest in possessing Commander Shepard's body once he's been killed.

Harbinger's goal is to use the Collectors to kidnap humans and use them to create a humanoid Reaper robot. At the end of the game, Shepard and friends destroy this Human-Reaper and blow up the Collector's base. Harbinger is then forced to lead the Reaper invasion manually by slowly traveling across the Galaxy towards civilization.

In Mass Effect 3, Harbinger is still the leader of the Reapers but has a much smaller role. His only actual appearance is during the final mission, where he appears on Earth and attempts to kill Shepard himself along with some other Reapers by shooting at him. Harbinger fires a powerful laser beam at Shepard which always hits him and injures him but does not kill him, but Harbinger assumes it did kill him and leaves. Afterwards, Harbinger, along with all other Reapers, is either destroyed or leaves the galaxy forever depending on how the ending plays out.

Harbinger is best known by fans for his famous line "ASSUMING DIRECT CONTROL", which he says everytime he takes control of a Collector.