The Witness is a cyborg commander to the anti-Hegemony Cause. A mysterious organization, their only goal is to disrupt the Hegemony's actions. More on this in the Imgur album.
He is mostly metal and has some built-in features with innate inefficiencies meant to boost his performance far beyond that of any Hegemony combat robot.
The Witness is in the Gungeon to reassemble the Cause.
In short, his cowardice and adherence to the Oracle Device -- an AI used to tell probability and the future -- caused him to surrender one of the largest Cause battleships to the Hegemony. This caused the collapse of the Cause and his exile from its remaining ranks.
He intends to undo this. By ignoring the Oracle Device's repeated warnings (as it is present in his inventory), he boards the Hegemony battleship alone in a pod and must fight all the way through it in order to clear it out and fire its weapons on its Hegemony escorts. Wielding the dodge roll, his unmodified sidearm, and a less broken thermal paste attachment, the Witness's past is intended to be unique in its assembly.
An entire self-contained level, it will test the player's endurance against Hegemony troops against all odds and the Oracle Device's snarky remarks.
There is no final boss, but there is the bridge. Holding the ship's commander, the Witness will have to fight someone of similar ability and armament to himself.
Once he clears the whole ship, he will assign its weapons systems to target the escorts and leave the craft to return to commanding his own craft.
Successfully completing the Witness's past will unlock Truth and Regret.
The Witness starts with one heart container and four armor due to his technically frail nature.
Hegemony energy weapons have a negative synergy to the Overclocked Core, and always will consume twice as much ammunition.
The Disintegrator has a synergy with the Overclocked Core, decreasing its charge time and increasing its ammo efficiency.
His B-skin is an outfit similar to that of Neo's from The Matrix, and the premise of his past is also a blunt reference to it.
Just cause is a pistol with, generally, high knockback.
In sum: Relatively low damage. High accuracy, high stopping power and velocity. 30 shots to a clip. Relatively slow reload. Average fire rate, but this is boosted by Thermal Paste and the Overclocked Core.
The Overclocked Core provides a boost to movement speed and fire rate slowly as the trigger to a weapon is held down. This does not work on beam or charged weapons. A notable drawback of this is that ammo consumption will rapidly increase as the core kicks in. More than one ammo per shot will be consumed as such, capping out at five times the ammo consumption.
The Witness starts out with this item.
Thermal Paste has an active synergy with the Overclocked Core. It resets the negative effects of overclocking briefly, extinguishes the user, and provides a small buff to all energy weapons (reload and fire rate) when used.
The Witness starts out with this item.
A past item.
Truth, or the Red Pill, will essentially force the user into a state of massive challenge. It increases loot drop chance and damage dealt, but also increases enemy bullet velocity and the player's curse. Every floor, Truth becomes harder to swallow; as such, the player will gain more curse. This also increases loot chance and a mild buff to damage dealt.
A past item.
Regret, or the Blue Pill, will remove all of Truth's effects (including the perks) except for the curse. Curse is only halved, however. Regret will only appear once on the floor following when Truth was used. It always appears by room drop.