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: The Azure Fortress.

Completing this level leads to E3M5: The Ophidian Lair.

Walkthrough
Beyond the pillars to the right, pick up the Ethereal Crossbow. Go to the newly opened room and pick up the yellow key. Go up the stairs to the southwest and go through the yellow door. On the other side, there is a rough corridor making a ninety-degree turn north in the distance. Go to the end and open the wooden door.

If you need ammo for the Phoenix Rod or the weapon itself, past the green door, turn left to the window, then left again and you will see a door. Inside, you will find Flame Orbs and a Phoenix Rod. Go up the stairs with a carpet, pick up the Bag of Holding, and the door behind it will open, revealing the green key and some disciples. Pick up the key, and another hidden room will open containing Mace Spheres. Go through the green door. In the first room, there are four red pedestals. Continue your way downwards, until you reach a crossing. Enter the next hall.

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 (a disciple will attack as soon as you pick up the key). Now you are in the middle of the water area you have seen from the three previous halls. Proceed to the inner circle and locate the blue door. After entering the door, two iron liches (one on the two easiest skill levels) will attack you. Quell the opposition and use the portal to get to the next level - The Ophidian Lair.

Secrets

 * 1) When you have entered the corridor behind the yellow door, proceed until you reach a step with a dark and blinking lighting. The northern wall has a decorative mask on its top. Press the wall to reveal a room with a Chaos Device and a varying amount of Quartz Flasks.
 * 2) Beyond the right angle, you will find a similar step. Open the western wall to reveal a Ring of Invincibility and a collection of ammo. In both previous secret rooms, there are also ophidians so beware.
 * 3) In the first room behind the green door, step on any of the red pedestals to temporarily make the room with the Dragon Claw accessible.
 * 4) At the next crossing, you will see a wall with the trident symbol on it. Press the wall to obtain the Gauntlets of the Necromancer.
 * 5) In the center of the level, use the teleporter with the Wings of Wrath to reach the surrounding water area, along with its goodies and iron liches. When you are ready to leave, look for a masked alcove in the eastern wall. It has a door that leads to a room with an Enchanted Shield and a teleporter back to the start of the map.
 * 6) When you arrive there, you can notice that a door in front of you has opened revealing a secret room with an Inferno Orb and a Mystic Urn.
 * 7) As you step onto the elevation with the Mystic Urn, a potentially empty room will open nearby. Go through the whole map again to the blue door to exit.

Firemace
In case the Firemace has appeared at the level startup, you will find it at one of four different positions. In order of appearance, they are located If the weapon did not appear, the next chance to get it is on E3M6.
 * in secret 1.
 * in a disciple chamber in the northwest corner of the blue key hall.
 * in the core circle of the center.
 * in secret 7.