Objective: Assassinate Otto Ackermann
Enigma Codes: 5
Special Requirements: Contraption
You start this mission in the town outside the wall. While you can enter the same way you did in the Campaign, there are a lot of enemies waiting for you. Instead, look for a way to use your contraption. For instance, there's a spot on the other side of the alligator farm building where you can use the Constrictor Harness's ability to move through a pipe. This puts you into the wall on the lowest level.
Head right, using cover as you go to avoid the Lasergewehr turret at the end. Rush up the stairs to clear out the Soldiers at the turret, then continue up the nearby stairwell to the next floor.
Advance along the first floor, clearing out enemies along the way. Use the control rooms on the side to avoid several enemies. Your goal is to reach the far end and take the stairwell up to the second floor.
The Überkommandant is in the section at the top of the stairwell. Kill him and grab the Death Card. Also check for a few Collectibles in this area that are only available during this mission. Once you have what you need, return to Evas Hammer.