Level 23: Unholy Temple: 3 Secrets

At the start of the level, eliminate all Arachnotrons to access blocked teleporters. Step through any teleporter to reach the level above. Once there, defeat all Spectres. Proceed counter-clockwise along the path until you find a lift to the level above. If bars block the lift, you must kill all Spectres to remove them. Lower the lift, board it, and ride it to the top. Turn around to find a platform with a Laser, two Energy Cells, and two Energy Cell Packs. Shoot the panel on this platform with your Pistol, Shotgun, or Chaingun. The platform will descend like a lift; quickly run to it before it ascends again. If you miss it, use one of the two teleporters in the water level to return to the lift. Stepping onto this platform grants credit for a secret.

From the first secret, continue through the level until you reach the Red Door and the Red Key. After opening the Red Door, enter the room and kill all Hell Knights/Barons of Hell (depending on difficulty) to create staircases leading to a higher perimeter ledge, which also allows access to the Yellow Key. Go to the staircase that leads directly to a wall. At the top of these steps, press C-Right and examine the wall. It will lower, revealing a hidden area containing a Rocket and three Boxes of Rockets. Entering this area grants credit for a secret.

From secret #2, progress until you reach the Yellow Bars and the Yellow Key. Open the Yellow Bars and proceed through. Run down the hall to jump over the pit and enter the room across from you. In the center of this platform is a pillar. Position yourself on the side of the pillar with only bricks, not a switch. This is a fake wall; walk through it to be teleported to another ledge in this room. This secret area contains several Rockets and a Soulsphere.