Harbinger (Collector)

Presumably due to possessing the Collector General directly, Harbinger can also control an individual Collector soldier in combat, this soldier gains a substantial advantage in strength, as well as the use of biotic abilities. The soldier whose body is possessed by Harbinger starts to crack open showing magma like appearances on the skin.

Capabilities
Possession

When Harbinger possesses any Collector trooper in the fight, even if the host was near death (almost no health), this Harbinger-Collector would still become a full health unit, with fully-charged barriers and armor.

Offensive

Harbinger will advance and attempt to engage Shepard at point-blank range. He possesses an extremely powerful and unknown biotic attack, which can penetrate thin cover, and cause Shepard to stagger back.

Defensive

Harbinger possesses extremely strong biotic barriers and armour.

Tactics
General Notes Class Specific Notes
 * When fighting Harbinger, it is best to keep at a distance, since his ranged attack is slower than the average biotic/tech abilities. His shots are capable of stunning a character in one hit and can quickly bring down the average squad-mate in close quarters. He is also capable of possessing multiple Collectors in a single fight so it might be better to deal with the weaker minions first before focusing on the master, provided there is sufficient safe distance between Shepard and Harbinger-Collector.
 * If you strafe left and right while in cover, almost all of Harbinger's attacks will miss you, including the slow shot that knocks you out of cover, even at point blank.
 * Although the Harbinger-Collector is a powerful foe by any right, during the short time it takes to possess a Collector trooper, it typically floats above any cover, not moving or attacking. This presents a window of first-strike opportunity, giving you a chance to quickly end a fight. For example, a well coordinated Warp, Reave and/or Concussive Shot during its transformation phase can sap away its barrier and even some of its armor. If your squad uses Armor Piercing Ammo, it will go down even faster. Once the Harbinger-Collector loses its armor, it will be dead, though Harbinger can possess another minion right after, if there are still any surviving Collector troopers in the field). Otherwise he is likely to join the fight with the next wave of Collector troopers.
 * If done correctly with Incendiary Ammo, a soldier Shepard can strip its defences away quickly using the M-76 Revenant in close quarters

Battle Quotes
"This hurts you""Preserve Shepard's body if possible.""You will feel pain, Shepard.""I know you feel this, Shepard.""Neutralize Commander Shepard.""If I must tear you apart, Shepard, I will."