Klaus, the new quirky A.I. robot in Mauer Der Toten, certainly has its uses. Not only is he good at clearing hordes of zombies with you, but he can also revive you when downed and have some other uses during the main easter egg on Mauer Der Toten.
In this guide, we walk you through how you can build Klaus and fully upgrade him to make him as strong as possible. Note that we did not include the easter egg head gear upgrade in this guide as it is not relevant in this case. The headgear upgrade is only useful for the main quest on Mauer Der Toten.
This guide solely focuses on building Klaus and fully upgrading him. The guide continues assuming you've already turned on the power and activated the pack-a-punch machine.
There are two things you need to build Klaus - Robotic Hands and a Battery. This is how you can get them.
First, you need to apply the Brain Rot ammo mod on one of your weapons.
Then make your way to Hotel Room 305. You will find a barricaded room here.
There is a set of robotic hands on the corpse inside the room. We need these to build Klaus.
Shoot a zombie near the barricaded door and turn him. The zombie will break open the door giving you access to the room.
Interact with the corpse, and you will pick up the robotic hands.
Continue playing the game until you reach Round 10. On Round 10, Krasny Soldat will spawn.
Kill him, and he will drop a Battery. Pick up the battery.
Now you have everything you need to build Klaus. Make your way to the safe house just past the Mule Kick perk machine and interact with the robot inside the safe house.
Klaus will be activated and get up. You will also get a remote control to command Klaus wherever you want.
Note that for the time you have Klaus activated, your tactical equipment will be dropped, as the remote control is given as tactical equipment.
You can upgrade Klaus a total of three times. Every time you upgrade Klaus, he gets a stronger weapon with an increasing tier of pack-a-punched weapons. On the second and third tiers, Klaus' appearance also changes.
Tier 1 Upgrade
The first upgrade is relatively simple. For the first upgrade, you need to find a microwave dish in the debris around Checkpoint Charlie. It is the same area where we have the pack-a-punch machine.
Keep digging the debris near both the sniper towers until you eventually get a microwave dish as a drop.
Pick it up and make your way to the Garment Factory, where the upgrade station is.
Interact with the upgrade station to install the microwave dish.
You will also notice that the screen on the upgrade station is red. We need to turn it green in order to upgrade Klaus.
To do that, you need to get kills with Klaus. Get Klaus in an open area and train zombies around him. He will kill zombies effectively.
You will know you have enough kills when you hear a distinct and unique sound in the background. You'll know when you hear it. Be on the lookout for a unique "whoosh/swish" sound effect while getting the kills. The screen will turn green when you hear that sound.
Return to the upgrade station in the Garment Factory and command Klaus near the station. Klaus will go to the upgrade station.
Once he is in, you will have to defend him for a total of 1 minute as he upgrades himself.
A lot of zombies will spawn, including the Disciples. If you already have the CRBR-S wonder weapon, then this step should be a cakewalk.
When the timer ends, Klaus will come out with a pack-a-punched weapon.
Tier 2 Upgrade
The for the second and the third tier upgrade, you need the blacklight. You can get your hands on one by going to the Switch Control Room next to the Mule Kick perk machine.
There is a locker with the number "0" on the wall on top of it.
Command Klaus near the locker, and he will punch it open, revealing the blacklight.
Pick it up and you will notice the color of your flashlight change from white to light purple.
Now, you need to find two electrical boxes with Klaus' face on the wall beside them.
Klaus's face can only be seen using the blacklight we have already acquired from the Switch Control Room.
There are six electrical box locations, and Klaus' face can randomly spawn next to any two of these electrical boxes.
The following are the box locations:
Box Location #1
The first box is found on the wall near the Tombstone Soda perk machine on the 5th Floor Apartments just below spawn. The wall is directly next to the zip line leading towards Hotel Room 301.
Box Location #2
The second box is on the wall next to the Stamin-Up perk machine in the Hotel Lounge right after you pass by Hotel Room 305.
Box Location #3
The third box is on the wall of the Ghost Station, just past the Deadshot Daquiri perk machine. You can get here via Service Passage in East Berlin Street. It is to the right as soon as you leave the Alley.
Box Location #4
The fourth box can be found on the wall in the Maintenance Tunnel. You can see it straight ahead of you as soon as you go through the broken walls coming from the Switch Control Room, just past the Mule Kick perk machine.
Box Location #5
The fifth box is in the Blasted Suite located on West Berlin Street. You can get here via Sewer Access after passing the Power Room. It is building with the "Der Dozent" sign to the left of the Trial Computer.
Box Location #6
The final location is directly in front of the fifth box location, but at the Der Wunderfizz perk machine-building base. You will find the box directly under the "Cafe Muller" sign.
Command Klaus near the electrical boxes with the head icon, and he will punch them open, revealing the floppy disk inside.
As mentioned before, there are two boxes with the head icon next to them. After collecting both the floppy disks, we can upgrade Klaus.
We found the first one in the blasted suite.
The second one was found in the Maintenance Tunnel.
Make your way back to the Garment Factory and command Klaus next to the upgrade station.
Once Klaus is inside the station, interact with the station to insert one of the floppy disks.
As soon as you interact, Klaus will begin upgrading. This one won't take 1 minute and won't spawn enemies.
Once Klaus upgrades, his appearance will change, and he will come out of the station upgraded to tier 2. Klaus will have an "emo" look to him.
Tier 3 Upgrade
If you've collected both the floppy disks, it is straightforward to upgrade Klaus to tier 3, which is the final upgrade. All you have to do is command Klaus back into the upgrade station.
Once he's in, interact with the station to insert the floppy disk. He will upgrade to tier 3, and his appearance will change once again. This time, he will be rocking the notorious Ronald Raygun look.