[9-15] E2M4: The Ebon Fortress

Right from the start, you'll want to hop down into the water. Head towards the right side and look for a cave entrance. It's right next to where you'll find a grenade launcher. Go inside this cave and continue into the next watery area. Take the entrance on your left, and then immediately turn left once you're through it. You should see a platform ahead with steps, and some high dragon windows to your left and right. Keep going straight until you hit a wall, then turn left. Follow this passage until you reach an elevator. Ride it up, cross the bridge into the next room, head down the stairs, turn around to your left, and go into the small inlet right next to the stairs. Shoot the wall here – it'll open up to reveal rockets and a valuable 200 health boost.

From that spot with the rockets and health, go back up the stairs and turn right. You'll see a wooden floor that's slanted against the wall. Turn right again and look towards the wall in front of you. There's a section made of wood that you need to shoot. Once you shoot it, it'll open up, revealing a tiny ledge along the left wall. This ledge is crucial for getting to the next area.

In the room where you'll eventually find the silver key, get off the moving platform. Turn right and head into the gap that has toxic slime below it. Swim down and then to the left. You'll discover a secret area containing the powerful red armor.

Let's revisit the start for another secret. Hop into the water and hug the wall to the right of the island where the grenade launcher is. You'll start to sink down into a secret area that holds Quake Damage (likely a power-up) and yellow armor.