Your goal in the Pain Maze is to defile the altars of Shub-Niggurath. Unfortunately, she’s throwing everything she has at you at this point. Dozens of spawns and a handful of vores will cause you endless grief. As you find the secret areas, you may want to leave the items for when you’ll really need them - in several rooms, a Quad Damage or a Pentagram of Protection will seem like your only hope.

This small button in the first large room opens a secret door along the back wall

Secret Area 1
In the very beginning, take the Quad Damage and the 100 health kit. In the first blue-tiled room you come to, there is a small star button on one of the pillars. Press it to open a secret area on the back wall, where an elevator will take you up to some ammo. There are some monsters up here, but disposing of them now - in your enhanced state - will make your work in the altar room below easier.

The Silver Key
After defiling the first altar, turn around. A small area containing the silver key will have opened. Jump across to get it.

Stand on the back beam, near the Quad Damage, and shoot the yellow circle on the ceiling. The beam will raise and you can grab the red armor

Secret Area 2
Jump into the pool in the passageway to the altar room. Note the small open area just above you as you turn the corner and begin to descend. Swim up to this area, where you’ll find a biosuit, a thunderbolt, and some health and ammo.

The Gold Key
In the large green room filled with spawns, press the four star buttons located on the pillars to access the gold key.

The discolored section of this underwater column is a door leading to the goodies pictured here

Secret Area 3
In the central pool area, examine the base of the island from under the water. One side is green instead of brown. Hit this area to receive some cells, nails, and a Pentagram of Protection.

Secret Area 4
After activating the elevator with the gold key, notice the red armor on the elevated platform. Make your way to the beam against the wall directly below this platform. Look up and shoot the yellow window on the ceiling. This will cause the beam to rise and allow you to grab the armor. There is also a Quad Damage located on a nearby beam.

At the second unholy altar, there is a Quad Damage in the back right corner that is easy to overlook. There is also a 100 health kit located on the far side of the altar itself.