- This level occupies the map slot E4M2. For other maps which occupy this slot, see Category:E4M2.
You begin the level on the south-western bastion of a square fort. From there you may see the inner blockhouse structure patrolled by ophidians, surrounded by a moat full of sabreclaws, and throughout the gratings you'll get a glimpse of the slime lake surrounding the whole level. If you think that you can just sit there and fire at the ophidians, taking cover when needed, you're about to realise that the level is constructed to prevent you from doing so. There is no corner of the bastions that gives complete cover from the ophidian shots and there are fire gargoyles ready to ambush you from the windows. There are flocks of gargoyles (both types) in each of the other 3 bastions and they'll come as soon as they spot you. Moreover, a bunch of disciples is located on the western, northern and eastern ledge, looking over the lake. They are extremely difficult to attack from the bastions and you don't have much ammo to waste right now.
If you've never learned the circle strafing technique so far, this is the level to practice it extensively. Start circling around the perimeter while firing at the ophidians as much as you can. Don't stop moving and they won't hit you; it's very likely they'll start some infighting with the gargoyles instead. Watch out for obstacles, especially the pillars marking the blue door, and for the sabreclaws emerging from the moat. Don't allow anything to block your movement or you'll become an easy target. The need for strategy in this part is very dependent on how you came out from E4M1: Catafalque (Heretic); if you're low on ammo, you have to collect the supplies in the area and use them wisely. If you do so, however, then even from low health it should be possible to recover from zero ammo, armor and power-ups, to leave the level as a very wealthy heretic.
After cleaning out the area, look for a teleporter that has become accessible on the north-eastern bastion, close to the green door. This will bring you inside the blockhouse, in the north-eastern corner. In the middle you will see a raised structure with many ophidians and the yellow key on top. The surrounding water pit is crowded with sabreclaws and more ophidians. Shooting the numerous enemies from the corner is not a good idea, it's better to jump down and start circle strafing around the stone pyramid and shoot at everything that moves. It is easier to do it here than it was in the outer ring. When everybody is dead, get as close as possible to the yellow key structure, then get out from the teleporter you came in. Now a new teleporter is accessible in the north-western bastion, leading you to the corresponding corner inside. You'll notice that another stage of the central structure has lowered and the elevators to north-eastern and north-western corners are both working. Once again, get as close as possible to the yellow key, then get out from the north-western teleporter. You have to repeat the procedure until the south-western and south-eastern teleporters (and corners) become accessible and eventually you will pick up the yellow key.
The yellow key allows you to enter the narrow walkway surrounding the blockhouse, where a lot of goodies and the green key wait to be taken. Unfortunately, as soon as you enter the walkway passages will open, releasing all of the disciples on the western, northern and eastern ledge of the level, so be careful while exploring the walkway.
Beyond the green door you'll find the blue key, guarded by several Iron Lichs and a Maulotaur. Now you should have plenty of weapons and ammo, including the Phoenix Rod, so the Lichs won't be a problem. To easily defeat the Maulotaur, lure him out of his lair. Most likely he will enter the moat around the blockhouse; there he'll be almost inoffensive as two of his attacks cannot harm you if you shoot from above. Inside the blue door room there's another Maulotaur that can be dispatched with the same trick. At this point the exit is protected only by a switch and by the last ophidian.
No official secrets.
The following area is not counted as a secret:
- To get into the surrounding sludge lake, you can go to one of the three ledges pointing into the lake. The area around the door is raised slightly. When standing on this raised area, you can get onto the ledge and jump into the slime. Another way is to let the tornado attack from Iron Lich hit you near the ledge. There is plenty of health to keep you going, despite the harmful slime, without using up items too eagerly. Just below the eastern and western ledges are pairs of wings, one of which must be used to get back into the fort.