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, the Harbinger-Collector will become a full-health unit, with fully-charged barriers and armor, even if the host is near death.

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. The attack, when both spawned and generated when it hits cover or its target, resembles a biotic Singularity. Harbinger can also spawn biotic attacks similar to Warp that drain Shepard's shields and health significantly. The higher the difficulty setting, the more he will use these abilities. On Insanity difficulty, his biotic attacks can become a non-stop barrage. Harbinger also has a short-ranged splash attack which is similar to the Praetorian's Death Choir. It can deplete Shepard's shields in a single hit, if Insanity difficulty level is chosen. In addition, this deadly attack has an incinerating effect that will cause Shepard to stagger back, which could be a death sentence on higher difficulty levels.

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 ability. 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.
 * Although it would be wise to take out Harbinger quickly, its even more useful to take out all other Collectors first so that once you defeat Harbinger, there are no others for him to possess until the next wave of enemies.
 * 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.
 * Another trick is to aim right before Harbinger's Singularity hits cover and then go back into cover. This will cause it to arc over you.
 * 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, so it is recommended such powers are mapped sequentially, and used in succession . 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.
 * Harbinger is susceptible to Flashbang Grenade's effect and cannot use any of its abilities while Flashbang Grenade is in effect. A good strategy is to bring Kasumi with Improved Flashbang Grenade to neutralize Harbinger while you and your squadmates focus on the other Collectors.
 * If you have used Dominate just before the target is possessed, you will have temporary control of Harbinger after the transformation.
 * Oddly, Harbinger will sometimes possess a Collector that is under the effects of Pull. If this happens, and the Pull wears off over an open space, Harbinger will fall to its death.
 * Harbinger typically possesses the weakest or most wounded Collector on the battlefield; because of this, it is important to finish off wounded Collectors quickly before they are possessed.
 * Harbinger's possession "cooldown" is much faster during the assault on the Collector Base, making it more likely that you will encounter it multiple times in a given firefight.
 * Harbinger is immune to Stasis; however, just as with Dominate and Pull, Harbinger will sometimes possess a Collector that is under the effect of Stasis. In this case Harbinger will still be immobilized until the Stasis ends.
 * If done correctly with Incendiary Ammo, a Soldier Shepard can strip its defences away quickly using the M-76 Revenant in close quarters.
 * On lower difficulties, the Widow Anti-Material Rifle will often destroy it with a single headshot, especially with the bonuses of a Soldier's Adrenaline Rush or an Infiltrator's Tactical Cloak.
 * An Engineer's Combat Drone has a short enough cooldown that Harbinger can be kept fighting it almost continuously, at least with fully-evolved Combat Drone and Tech Mastery powers and the Tech Cooldowns upgrade.
 * If you are an Adept, Singularity will hold Harbinger in place, allowing you time to take out its barrier and armor with Warp.
 * Because of its deadly close-range area attack, on high difficulty levels a Vanguard should never Charge Harbinger unless it has already been damaged enough that it can be killed immediately after the Charge.

Battle Quotes
Once Harbinger possess a Collector on the battlefield, it has a series of quotes that it will say.