Bergusia Forge is the last forge visited by the Guardian, as well as where the last key for the mystery box is forged. This is also a Fallen-based forge and has some dangerous areas where the player can fall off of.
It is the same goal as the other three forges. Three waves packed with enemies and batteries to throw.
These drones are the easiest to find. One is at the back left of the map from where the player enters, close to the ground. The second spawns on the right side and is easiest seen at the red pipes close to the fog where the player walks in.