Kill 25 enemies while in stealth using the Trench knife. Unlocks the "Red Bear" mask, "Short Barrel", "Suppressed Barrel", "Short Mag", "Folded Stock", "No Stock", "Solid Stock", "Heatsinked Suppressed Barrel" for the Patchett L2A1 submachine gun," Barrel Sight 44", "Damper.L 44 Nozzle" for the Broomstick pistol, "Red Sun" material and "Death Dealer" pattern.