[9-3] E1M2: Castle of the Damned

You'll start off heading down some stairs. Instead of just walking forward, take a jump off to your right into the water. You're looking for a lit green wall; shoot it, and a passage will open up. Follow it, and you'll eventually surface.

There's another way to get to this secret area, too. If you find the bridge with that big red symbol over it, you can jump off and swim underneath it, heading away from the symbol. You'll swim under an arch and find yourself in a small room with a ramp on the left. Head up that ramp.

Now, let's talk about the main path and another secret. From the start, head forward until you hit a wall. Turn right, go forward again, then turn left. You'll see a bridge over some water, with a large red symbol on an archway above it. Go onto this bridge. To your left, you'll spot a double-barreled shotgun. Jump off the bridge near it and swim underneath where the shotgun is. Keep swimming under an arch and then turn right. Follow this passage – there will be a bridge above you the whole way. Eventually, you'll reach a pool. On the left side of where you enter this pool area, there's a wall with a symbol high up on it. Walk right up to it, and it'll open. Inside, you'll find 25 health, a box of nails, and a slipgate that will take you to the ledge opposite where the double-barreled shotgun was.

Back to the main route: cross the bridge with the red symbol. Once across, turn right and go through the door. Take a left turn and start climbing the staircase. As you ascend, you'll notice a column to your right, about midway across the room. Go to the side of this column that faces outward. You'll see a small stone plate on it; push it. A door will open up to your right, revealing a Quad Damage power-up. Grab it – it's super useful for clearing out tougher areas.