- "Mission log entry forty five: I am over the site looking down through the open door. I can see a weird distortion below me like a localized Aurora Borealis. I would normally cancel the operation, but we don't have time. Luckily, I have taken experimental weaponry version three that no one has seen before from my previous mission. Never say never, Peter."
- — Cipher on Der Eisendrache
The weapon consists of the GKZ-45 on the left, which shoots yellow clouds of energy that slow down zombies, and the Ray Gun Mark lll on the right, which shoots thinner versions of the Ray Gun projectile which do not cause splash damage. Running through the yellow cloud will cause the player to run quickly and running through the purple cloud will cause the player to go even quicker much like the Overdrive specialist ability or the spores shot by the KT-4 on Zetsubou No Shima. Similar to igniting gas with a spark, shooting the yellow energy with the Ray Gun Mark III will cause it to become a black hole similar to the ones created by the Gersh Device and the Apothicon Servant, but with much lower damage (one-shot kill until round 25-30), smaller range, and shorter duration. Rather than being sucked into the black hole, zombies affected will float up and dissolve into a purple mist, similar to the effect of the Wave Gun, Storm Bow and Skull of Nan Sapwe.
Maelstrom of Eris
When upgraded in the Pack-A-Punch, it becomes the Maelstrom of Eris. The weapon carries five rounds in the GKZ-45, 30 rounds in the Mark III, and initially 210 in reserve, although it will receive 215 when the player receives a Max Ammo. The upgrade appears red, provides additional ammo, and increases the duration, range, and damage of the black hole effect. The Ray Gun Mark III upgraded will fire red beams, similar to its predecessors, but the GKZ-45 continues to fire yellow balls of energy.
GKZ-45 Mk3 vs. Maelstrom of Eris
- The GKZ-45 has a red soviet star on the right side, and the Ray Gun Mark III has a raised star on the back of the weapon in between the four yellow coils.
- The Ray Gun Mark III has iron sights, but the GKZ-45 does not.
- In the trailer for Gorod Krovi, when the box is used, two Ray Gun Mark IIIs can be seen instead of a single Ray Gun Mark III and the GKZ-45.
- The reserve ammo of the unupgraded weapon, both starting and after a Max Ammo, is not divisible by the magazine size of either the GKZ-45 or the Ray Gun Mark III. The initial reserve ammo count of the Maelstorm of Eris is divisible by both weapons, but is only divisible by the GKZ-45 when the player receives a Max Ammo.