Harbinger

Harbinger is a Reaper, who resides in dark space with the rest of the Reaper fleet. It is the overseer of the Collectors' operations, frequently possessing individual Collectors to fight battles personally. Harbinger's involvement first began in Mass Effect: Redemption, when it made a deal with the Shadow Broker to gain possession of Commander Shepard's body. This plan ultimately failed, and Shepard was resurrected by the Lazarus Project.

During the events of Mass Effect 2 Harbinger is the mastermind behind the Collectors, appearing to permanently possess the Collector General. It directs the Collectors to abduct the entire population of human colonies in order to use their genetic material to create a Human-Reaper.

While controlling the Collector General, Harbinger is capable of possessing any individual Collector, often doing so when the Collectors are engaged in combat with Shepard. While controlling a Collector, Harbinger is able to speak through them, usually to command other Collector troops, or threaten its opponents. However, the process of possession appears painful or traumatic to the possessed Collector, and it often disintegrates when defeated. The effect is very similar to Sovereign's possession of Saren Arterius.

Harbinger shows a personal interest in Shepard, particularly a continuing interest in recovering the Commander's body, as it orders the Collectors to recover Shepard's corpse intact if possible. This could be another consequence of Shepard destroying Sovereign, and drawing the Reapers' personal attention as a result, or relate to the Reapers' orders to gather human genetic material.

After Commander Shepard's team assaults the Collector base and destroys the still incomplete Human-Reaper, Shepard can either destroy the base completely, or purge the base of all life. Both options will result in Harbinger relinquishing control of the Collector General and vows that the Reapers will "find another way." Harbinger is then seen with the rest of the Reapers in dark space and appears to either observe the galaxy or begin moving toward it.