E3M7: The Chasm (Heretic)

E3M7: The Chasm is the seventh level in The Dome of D'Sparil episode of Heretic.

Secrets

 * 1) Once you have entered the two first wooden doors, you will come to the yellow door. Opposite, there is a picture of two horsemen. Press the wall to reveal a mosaic room with a varying amount of weredragons. Hit the switch to open the western disciple wall and enter the teleporter that was revealed. You will end up in a small room with an Energy Orb and a sabreclaw. Activate another switch to make a new teleporter available and use it. The teleporter will take you to a room that is identical to the previous one but holds a Dragon Claw instead. Repeat the aforementioned actions yet a third time to return to the mosaic room.
 * 2) The chamber of the maulotaur holds a teleporter on both its western and eastern side. Step on the former to end up on a ledge in the previous room. Hit the switch there and return to the chamber to see that a pillar with a Quartz Flask has been lowered. Take it, and the horseman picture will open revealing a room with a Hellstaff and a varying amount of disciples.
 * 3) By using the eastern teleporter in the chamber, you will eventually get to the green key. You can notice that the southern wall in the key room is misaligned with those surrounding it. Press it to discover a bright area with many timebombs.
 * 4) After entering the green door, you will descend to an underground area. The center part there is sewer-like with a water surface and hanging moss. Around the center, there is a small network of cave corridors. When you enter the one with stalactites and reach the end of its U-turn, you will find an illuminated section. Press the wall opposite the decorative torch to find a room with a Phoenix Rod.
 * 5) Follow the stairs next to the previous secret to find an outdoor area. There is a bridge above a lake of sludge. To make things worse, there is a strong west wind. While you cross the bridge southward, you need to compensate the wind by running to the southeast. Straferunning is more effective but not necessary. At the other end, you will find the blue key along with the Wings of Wrath. Activate the wings and travel to the western end of the sludge lake. There is a ledge that leads to the iron lich room of the corresponding side. Collect the heavy ordnance there. You may want to return via the teleporter on the bottom of the sludge lake as it holds a Shadowsphere.
 * 6) The eastern end of the lake has a similar ledge. It is connected to the second iron lich room and has a similar content, but when you enter the area, a room with two ophidians and a varying amount of Mace Spheres will be exposed about halfway the corridor.
 * 7) If you fire a single shot after stepping into the blue key room, you will wake four sabreclaws back at the underground area. When you return there, get rid of the enemies and start exploring the zone. A door has opened in the southeastern wall of the sewer area. Beyond, there is an area that holds a Mystic Urn.
 * 8) A second door has opened in the western wall. There is a Map Scroll in a room.
 * 9) A third door has opened in the eastern cave corridor. A Tome of Power can be found in the exposed area.
 * 10) Finally, a fourth door has opened near the staircase of the green door. There is a Chaos Device in a room.

Bugs

 * Linedefs 84, 89, 143 and 154-160 of the underground area all miss their upper textures because they have been set on the wrong side. Thus, there is visual distortion on the ten wall sections that are 16 map units high.