[9-9] E1M8: Ziggurat Vertigo

At the start, grab the Pentagram of Protection. Dive into the lava near the bridge and swim beneath it, away from the ziggurat. You will emerge in a small room containing a Quad Damage powerup, health, and a slipgate that leads back to the bridge in front of the ziggurat.

After passing through the silver key door, you will find a passage to the left and one to the right. Take the passage to the left and follow it to the end. On your right, you should see a wall with a dark border on one section. Shoot this section of the wall to open a door, which leads to two boxes of nails.