Armour and weapon gizmos charged with perks can be used to enhance the weapon's abilities. As a shieldbow, the augmented dark bow can hold 1 of each type of gizmo, allowing up to 4 perks. Dark bows augmented prior to 13 June 2016's update could hold two weapon gizmos; disassembling a level 2+ version or using an equipment dissolver returns one of each gizmo (it is unknown if this could be used to get a weapon-only perk on an armour gizmo).
Using this weapon in combat can gain experience to increase its level. Levelling the weapon will have no effect on its ability in combat, but it will improve the experience and materials gained for disassembling it.
The Augmented dark bow uses charges stored in the universal charge pack. When the charge pack runs out of charges, the item loses stats and gizmo effects, and can also no longer gain any equipment experience. Function will resume when the pack is recharged with divine charges.
Your current drain rate for a tier 70 two-handed weapon is given by the following table. It depends on your current reduction researched, the item level, and Efficient/Enhanced Efficient perk presence.