Heretic/E4M8: Shattered Bridge

This is the final level of the episode. When you leave the room you start in, immediately go back inside. A large compartment full of ghostly Golems has opened in the back. By taking care of them now, they won't sneak up on you from behind while you're busy outside.

The bridge
Outside is a large valley separated by a wide water-filled channel. A slow wind pushes you to one side. The namesake bridge, presently in pieces, crosses over. Golems swarm everywhere. First, go to the passageways at either end of the area, inside which are Disciples of D'Sparil that would otherwise have snuck up on you. As you fight the Golems on the other side, sections to the bridge will rise into place. This part of the level is a bit buggy: one or two sections of the bridge will usually remain lowered. But it's not a showstopper, because the gaps are just small enough to run across.

Labyrinths
Across the valley, on either side of a door beyond the bridge, are two groups of lifts that lower intermittently, with passages above that form a labyrinth. Thoroughly explore this area. Whenever you see a section of wall with a pattern on it instead of the plain gold/brown stone, it's a door or column that will open or lower when you activate it. The route past the door leads to a Yellow Door. At one point the labyrinth crosses over the route past the door by means of a pair of columns that lower when you activate them. Up in the labyrinth, on either side of this, look for doors leading into cages looking down into a small courtyard. Furthermore, concealed doors in the cages lead to a second pair of cages further in. By getting into these cages, you can clear out enemies ahead of time.

Yellow Key
Back outside, ride the lift up that was on your far right when you crossed the bridge, step into the passage above, then step back out and jump down from the lift. Next to the lift, in the corner, another hidden lift has momentarily lowered. Follow this path to the wide nook up on the wall nearby that you probably saw earlier. When you step out over the edge of the nook, a door at the back of the nook will open, with enemies and the Yellow Key inside. (Actually, only your point of view needs to cross over the edge of the nook for the door to open. It's easy to get caught by the wind and fall off, but if you're careful you can avoid this.)

Finale
Go to and open the Yellow Door, which leads to the small courtyard that the first pair of cages looked into. The switch in here momentarily lowers the back wall, leading to another courtyard the further pair of cages looked into. This wall can't be opened from the other side, so collect health and ammo as needed before continuing. When you're ready, go to the far courtyard and hit the switch here. The back wall will lower, with the final battle beyond. This is just a group of Iron Liches in a smallish arena, and isn't much trouble, especially with the nearby Phoenix Rod and many Flame Orbs available in the level. As with any group of enemies, fighting them individually as best as possible will cut down on the amount of weapons-fire you take. When they're defeated, the tall column in the middle of the arena will lower, with the exit portal on top. You have now completed the episode. The ending dialogue will assume you'll be playing the fifth episode next.