From Destinypedia, the Destiny wiki
Tech Packs can be found carried on the backs of any Minor or Elite soldier of the Shadow Legion, other than War Beasts. Sometimes units come equipped with them, but they can also be generated randomly. As long as the trooper has a pack, they will have a regenerating Resonant Shielding, identifiable by their orange glow. When the soldier is defeated, the pack will fly briefly through the air before landing, at which point it will open in a form similar to a Pyramid Spike and project a field. Shadow Legion troops that enter this field are tethered to the pack, which provides them with an Overshield as well. The pack will stay on the ground for a considerable time before dissipating, but can be shot and destroyed to deprive troops of their shields, which will also cause it to explode. The pack can also be shot while in the air, in which case it will take much less damage before exploding.
A Legionary carrying a Tech Pack
List of appearances