There are two Mastery Tokens hidden across “Nekravol - Part 1”, but only one of them hidden. You can now activate this hidden Secret Encounter. Look for a previously gated area that’s now open. Head out of the battle arena and back from where you came, beneath the two large spikes falling from the ceiling. When you do, you’ll hear a sound but won’t see any changes to your immediate area.
From there, jump over to the ledge, drop down, and activate the green skull switch. Right before it reaches the top, jump off the cage to the right and grab the climbing wall. To access it, first get onto the moving cages where you see a glowing green skull. In the battle arena in the third section of the Soul Factory, you’ll notice a ledge to the northwest of the room. Image: id Software/Bethesda Softworks via Polygon
