In the "Ground Zeroes" mission, rescue the prisoner to be executed and extract him via chopper

Clear the "Ground Zeroes" mission

Complete the first 3 towers of Quest mode

Complete Mission 2 (Any Difficulty Level)

Fully Upgrade A Single Stat Of Any Weapon In Campaign Mode

Complete A Mission In Co-Op Mode (Any Difficulty Level)

Collect An Armor Piece

Drain the Sewers

Reach rank 25.

Unlocked when the player completes the Workshop.

Unlocked when the player finds the Cyclops' bottle in the Carousel area.

Unlocked when the player completes Act I.

Unlocked when the player falls into the void on the way to the Cinema.