E3M9: The Aquifer (Heretic)

E3M9: The Aquifer is the secret level in The Dome of D'Sparil episode of Heretic, and can be accessed from E3M4.

Beyond the pillars to the right, pick up the crossbow. Go to the newly opened room, and pick up the yellow key. Go up the stairs to the south-west, then go through the yellow door. Once you reach a section which is dark, push the wall on the left, it will reveal a secret room with a Firemace. If you need ammo for the Phoenix Rod, or the weapon itself, past the green door, turn left to the window, then left again, you will see a door there. Inside, you will find Flame Orbs and a Phoenix Rod. Go up the stairs with carpet, pick up Bag of Holding, the door behind it will open, revealing the green key and some magi. Pick up the green key, another secret room will be opened with Mace Spheres. Go through the green door. In the first room, step on those red things, and a room with a Dragon Claw will open. Continue your way downwards, until you reach a crossing. Push the wall with the Sign on it, it will open and reveal a room with a Gauntlets. Pick up the Hellstaff, but beware of the ceiling as it will fall down. After the area is clear, pick up the blue key, and go through the portal (magi will attack as soon as you pick up the key). Now you are in the middle of the map, go around, if you want to kill the Iron Liches and get the pickups in the area between the outer ring and the center, use the teleporter with a Wings of Warth in it. After you are done, look for a section of waterfall deeper in the wall. It will lead to a room with an Enchanted Shield and a teleporter back to the start of the map. As you see, a door opened revealing a secret room. On the right of this room, you will see a painting. Touch it, and another room with pickups will open. Go through the whole map again, to the blue door. After entering the blue door, 3 Iron Liches will attack you. Kill them, and use the portal to the next level.