Call of Duty WW2 Zombies: How to Get Bloodthirst Tesla Upgrade Variation - needed for "Dark Arts" trophy & achievement.

PREPARATION STEP (BUILD NORMAL TESLA + LIGHTNING ROD DEFENSE):

Before you attempt this, do the normal main easter egg. You must complete the main easter egg up until the Lightning Rod Defense.

Step 1 (Use Brenner Head on Statue in Courtyard):
Kill a Brenner (flamethrower guy) and pick up his head. Now aim the head at the statue in the courtyard (left of the Lee Enfield sniper rifle wall-buy). You must press L2/LB to aim the brenner head. It will destroy the statue and reveal a battery.

Step 2 (Get Battery):
Shoot the battery with the normal Tesla Gun. Now you can pick it up and insert it in the courtyard right in front of the Lee Enfield wall-buy.

Step 3 (Kill 2 Big Groups of Normal Zombies with S-Mine Trap in Courtyard):
Kill 2 big groups of normal zombies with the S-Mine Trap in the courtyard. You can train zombies by running in circles around the courtyard. Try to kill 15+ per trap use. If you don't kill enough you may need to do this a third time. This charges up the battery.

Step 4 (Lightning Rod Easter Egg Step):
If you haven't already, complete the main easter egg up until the Lightning Rod Defense. Only after defending the Lightning Rods you can continue with the Tesla Upgrade.

Step 5 (Defend Battery):
Once the battery is powered up, pick it up (you'll know it's powered up because you can interact with it and pick it up). Insert it in the machine in the laboratory that previously gave you a part for the normal tesla gun. Hold the interact-button to close the hatch. Now you must defend the battery for about a minute or so. Zombies will attack you and also attack the battery itself. There's a health-bar on the battery, the zombies aren't allowed to destroy it.

Midnight Upgrade Complete:
After successfully defending the battery, pick up the part from the machine. Now you can return to the Tesla Upgrade Station in the Command Center (Bunker) to build the upgraded Midnight Tesla Gun.