When you have done all the work in the Maker's Forge, take the elevator to the Crossroads and burn a passage on right side, just behind Vulgrim.
When you go through a narrow tunnel you'll find yourself in the second part of a ruined city.
On the left side you'll find a sleeping gorilla, which prevents on access to an item.
Jump on the rock shelf on the right side to be able to jump to the levitating souls. On the right you'll find another item. The opponent at the very end guards access to one of the artifacts.
Use the passage on the right to go to the next location.