[9-18] E3M1: Termination Central

First off, head to the large platform that looms over a toxic pool. You'll find the Quake damage pickup here. From this platform, carefully hop off the edge into the toxic sludge. Swim straight down, and you should spot an opening in the wall near the floor. Swim through it – this teleporter will boost you up to 200 life and give you some other useful items.

Now, back on that same platform where you entered, find the spot between the two stairs on the side where pathways lead. Hop off the edge here. Look around, and you'll find an elevator that will take you to the very top of the platform structure.

Once you're up, turn so the Gold Door is behind you. Go into the opening formed by the metal boxes in front of you. Make your way to the highest point and shoot at the wall that looks a bit broken or out of place.

With the Gold Door still at your back, move past the metal boxes. To the left of the elevator, hop into the shadows ahead. There's a narrow ledge along the wall in this shadowy area. Once you're on it, turn left – you'll find the Quake Power-up.

From the very beginning of the map, after you descend the elevator and go down the first ramp to your left, look for a darkened section of the wall on your right. Shoot it, and it'll open up to reveal the red armor.