Once you have entered both side areas, there should be steps leading to both of the rocky ledges behind the buildings at the starting point. The next switch activates the cyberdemon, and stepping on his platform raises the bars so you can leave this area. Flip the switch in the back behind the inactive cyberdemon, revealing two arch-viles and another switch, and look out for the revenant horde that appears just behind the cyberdemon as well. You need to make a right at the intersection, and enter the pitch black room. Taking the northeastern teleport takes you to a blue area with loads of various monsters in some sort of T-shaped highway. The switch allows you to access the middle void, taking you back to the starting area. Finally, take the western teleporter inside and then press the last switch, releasing a myriad of monsters, including a cyberdemon in the center of the interior marble structure. This time you will have to contend with ghost monsters. Return inside and take the southern teleporter (directly in front of you) and again, press the switch behind you. Again, press the switch behind you, and you will release several barons of Hell and arch-viles outside of the temple. Take any teleporter outside to head back inside, then take the teleporter to the east. Press the switch behind you, and you will lower another teleporter inside the temple, but also release several arch-viles inside. Kill them and press on the pentagram wall in the back to lower a teleporter.
If you take the southwestern teleport, you will wind up in a marble section with various monsters. Each of those will take you to another section of the level. Now if you want to reach the exit, you must head through two hidden teleporters in the main central area, one in the northeast and one in the southwest - visible as "("-shapes on the map. If you attempt to grab the super shotgun, you will teleport into the chessboard and will be forced to fight the monsters before the door opens (but you will get the super shotgun anyways though). In the southern building is a chessboard-type setup. If you grab the backpack, two cyberdemons will activate. The north building has arch-viles, barons of Hell, and mancubi. The two buildings are optional, but if you need supplies, then enter these two buildings. One contains a rocket launcher and some ammo, the other one holds the exit. There are two buildings, and behind those buildings are rocky ledges. In the black void, you will be ambushed by various monsters. Sector numbers in boldface are secrets which count toward the end-of-level tally. Letters in italics refer to marked spots on the map.