Facet of Defiance

To reach this fragment, load into The Impasse and head into The Transgression. Make your way to the large opening that contains a statue of an impaled man, then turn left into the cave opening.

This cave's air is poisoned, so be sure to refresh your buff by shooting the nodes of darkness whenever needed. Make your way to the back of the cave and interact with the pyramid object to begin a combat encounter. In this encounter, you'll need to shoot eyes hidden throughout the cave to take down the shields of the enemies that spawn. Each wave has an increasing amount of both eyes and shielded enemies, so be cautious. After defeating three waves, head back to the pyramid object at the end of the cave to defeat a Tormentor boss. This boss drops a key, which will unlock the prismatic chest.