The Lightweight Power Armor, or Lightweight MkIII T-80d Power Armor, is the lightest, though weakest power armor in the wasteland. Though dubbed lightweight, it ironically isn't light. However, Fallen Angels troopers jokingly claim "it's like walking around naked" compared to other Power Armors. It can only be found used by Fallen Angel soldiers as they are the ones who manufactures it.
The Capital Wasteland Chapter of The Brotherhood of Steel found that it was harsh to walk long distances with the old T-45d Power Armor or even the newer T-51b Power Armor. In order to more easly travel large distances and use the enviroment to their advantage, they needed speed.
Thus, Project Light begun. The Project was lead by Senior Scribe Reginald Rothchild, (fanon) though by the time they could finish the project, the schematics was stolen by the rouge Brotherhood unit: The Fallen Angels in 2280. When The Fallen Angels escaped via the BoS Carrier VTOL and settled down in Lincoln, the technological experts of the unit were happy to find out that it wasn't far away from completion.
By 2281, it was complete and manufacturing of the Lightweight Power Armor started.
This power armor is the most agile power armor around. It doesn't burn through Agility points at all and you only need half the usual power armor training in order to use it, making it somewhat easy to become standard issue equipment.
The suit was made of a special bulletproof fiber and provided effective heat and moisture insulation, reducing both injury and stamina loss for the wearer. Attatched above the fiber, there's thin metal alloys used for the obvious purpose of protecting the user from even more punishment. This alloy is much thiner than any other power armor out there and while it protects the user from plenty of damage, it isn't near as effective as the metal alloys used in other power armors.
The armor also has an interior forcefield. While it doesn't block energy weapons, it absorbs some of the energy, allowing the user to use the power armor even longer before it has to be recharged. It also reduced damage taken from energy weapons by 5%. The helmet is also equiped with a Night Vision Screen and a Sound Indicator, making it easy to see during the night and know where the enemy is coming from. This power armor is the ultimate weapon for power armor based guerilla warfare.
Compared to combat armors used by factions all over the wastes, the Lightweight MkIII T-80d Power Armor is rather strong. But compared to other power armors used throughout the wastes, it's quite weak. It doesn't deter as much damage as other power armors, but this wasn't exactly the point of it either. The point was to be agile yet strong.
The Lightweight MkIII T-80d Power Armor can only be used by The Fallen Angels. There is an exception however. It can also be salvaged by characters (not entire factions) that has the Power Armor Training perk.