This is the 13th story progression achievement.
*** Spoiler - click to reveal ***After completing ‘Prisoner X’ go speak to Dogen to begin ‘Thy Kingdom Come’. You’ll then need to head to a marker in the Omnistat Tunnels to trigger a cutscene – after which you’ll be given another marker to the actual mission location, deeper in the tunnel system. Make your way down deeper underground and follow the path to get you inside the complex. Once inside follow the path through the complex, taking out a few guards on the way. Eventually you’ll trigger a cutscene, after which you’ll need to deactivate a terminal in front of you. Continue to the next marker to trigger yet another cutscene. Once the scene is over take out the guards then make your way outside and head for the cargo elevator to get you out of the area - making sure to keep sprinting to avoid incoming turret fire. Once the elevator stops there’ll be a few more guards who will jump down to meet you, plus a turret when you climb out of the elevator shaft. Once you’ve cleared your way follow the marker to wind up back in the main tunnel system, where the achievement will unlock. Return to the Tunnels hideout to wrap up mission properly with cutscene.