The Galvaknuckles are a kind of upgrade for your melee attack that can be found in the new Zombie map called Die Rise. They are fairly powerful and cost 6000 points so you’ll need to save up a bit. They are located quite close to the location of the first mystery box in the upside down building so you can take reference from our mystery box location guide in case you get lost.
First of all you need to get 750 points so you can unlock the large double doors underneath the two red staircases right in the beginning.
Follow the corridor to the left once they’re open and at the end of the hallway there will be a large broken section of wall through which you can drop down to some ruined stairs. Enter the room with the wooden furniture to the right and go across to the escalator.
After going down the escalator take the second right. You should find yourself on a ledge on the side of the building with a long drop on your left. Travel along the ledge to the next room and you’ll find another broken wall with a large section of rubble that acts as a slide. This slide will take you to the room with the mystery box.
Exit this room using the doorway on the right side and look up the hallway you find yourself in. You will see an empty elevator shaft. You need to drop halfway down this shaft to find the Galvaknuckles. In order to get to the room, drop down once onto the platform directly below, then once more to the platform on the opposite side of the shaft (the one with the hole in the wall).
Now from this ledge look to the left (so the opening in the wall is to the right) and drop down one last time in this direction. Go into the room to the left and you’ll see the Galvaknuckles on the wall opposite.