The Summoning Key takes up one weapon slot of the player who carries the artifact, and can be thrown. It must be thrown at 7 specific locations throughout the map, all being locations of Easter Eggs from the old maps. These locations are the following:
- Mob of the Dead: Look at the cells from the bridge on the wall opposite the Corruption Engine. Throw the Summoning Key at the poster inside one of the open cells.
- Verruckt: Looking toward the Corruption Engine, look left to spot a fountain with a machine gun mounted on top. Throw the key at the gun on the fountain.
- Shangri-La: To the left of the stairs leading up to the top of the temple, look left. There’s a Keeper statue, but further left there is a bright blue orb on a staff. Throw the key at this object.
- Origins: Go to the top of the hill in Origins (where the entrance down into Mob of the Dead is located) and look for a gravestone at about eye-level on a wooden catwalk.
- Der Eisendrache: Throw the key at the clocktower face visible just over the ceiling ruins when looking up from the Corruption Engine area, near the portal to Nacht der Untoten.
- Nacht Der Untoten: Go to the lower-level wall with a view of a crashed truck in the background. To the right of the truck is a red barrel. Hit the red barrel.
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Kino der Toten: Hit the huge chandelier hanging above the seating area.
After throwing the Summoning Key correctly in Kino, the teleporter has to be used again. All step in the teleporter and interact with it at the same time, which will teleport you to the arena again to complete the Boss Fight. It is recommended to read the next step beforehand, so you know what to do before entering the arena.