Heretic/E5M5: Hydratyr

You begin outside on a high overlook above a huge, deep water-filled area, most of the center of which is taken up by a tall battlement. Behind you is the Blue Door. Jump down and take a look around. On the far side of the area, along the outer wall, you'll find the Yellow Door up a wide stairway, and several overlooking areas well up on the wall.

Battlement
Go around to the side of the area that was to your right when you entered the level, and you'll find the entrance to the battlement. Inside is a tall tower, and two concourses of wooden platforms leading up and dead-ending, one along the inside of the battlement, the other encircling the tower. The entrance to the tower is ahead; follow the stairway inside up to a small elaborate circular room, where you'll find the Yellow Key.

Go to and explore the two concourses. On the outer one you'll find an Ethereal Crossbow. There's a well-hidden bonus available here, too. Jump to or climb up the inner concourse and go to the highest section of platform at the end. When you run off the narrow end of the highest platform (where the Bag of Holding is) facing the upper part of the outer concourse, it lowers a big lift along the high end of the outer concourse, leading up to the battlement. Get a running start and strafe left as you run off the edge and you'll make it to the outer concourse, then go to and ride the lift up. Although the battlement becomes accessible by teleporter later, you can get to a lot of items right away and clear out all the enemies on top, plus it might be easier to fight all those ghostly Undead Warriors and other enemies on the overlooking areas outside because you have more cover up here.

Big lava room
Go to the Yellow Door, fight the enemies inside the windows on either side if you want, and then go inside. In here is a tall hall leading left and right, a narrow wooden door at one end, and an overlooking area opposite where you entered. To either side you'll find doors going to those two side rooms the windows outside looked into. Look for and hit the switch inside one of the rooms: this lowers a lift leading up to the overlooking area in the hall.

Go up to the overlook. Here there are three doorways: the left goes up some stairs to a small room with a switch, and the right doorway down some stairs to a similar room and switch. The center doorway goes to a huge, long, deep lava-filled room with a walkway around the perimeter, a caged-in area up on the wall at the far end, and three pedestals down the center of the room. On the far pedestal is the Green Key out of reach on a second smaller pedestal. Watch for ghostly Undead Warriors and their more damaging red projectiles from the cage across the room. Note the two red-textured sections of walkway at the corners of the end of the room with the cage. They're lifts that lower when you run into or across the edge overlooking the lava. If you fall into the lava, these are your way out.

Inside the doorway is a switch that raises a walkway between the first and second pedestals. The upstairs/left-side switch back outside the entrance raises a walkway between the second and third pedestals; the downstairs/right-side switch raises a walkway to the first pedestal. Go to the column on the first pedestal and hit the switch on the back of the column. This lowers the Green-Key pedestal, allowing the key to be picked up, plus it opens four big side areas on either side of the room, releasing a bunch of enemies. When you step onto the third pedestal, it raises a walkway from here to the far end of the room.

Lava room bonus areas
There are some bonuses available. For each of the four side areas, if you step into one, the back wall lowers, with an enemy inside. If you step into that area, that back wall lowers, revealing another fenced-off area with an enemy and a teleporter. Sometimes the enemy (a ghostly Golem) will teleport away before you can kill it.

In between each pair of side areas, a tall deep nook also opened, with a switch at the back. Hit it, and that section of walkway nearby with the red texture will lower, revealing a small room. (Lowering the red-textured sections creates gaps in the perimeter walkways, because the sections stay lowered, but you can still clear them with a running start.) At the back of the small room is a hidden door to another room and a teleporter. The teleporter goes to the fenced-in areas inside the side areas, which are daisy-chained by the teleporters inside and eventually returns here. Items available include a Ring of Invincibility. To exit, you'll need to run across the lava to the walkway/lift. Make double-sure you run to the end of the room with the cage up on the wall, which is where the lifts actually are. (It's very easy to get mixed up here! You don't want to be stuck in lava at the wrong end of the room, trying to activate a "lift" that refuses to budge.) Both sides of the room work the same way.

Icky water
Go back out to the hall inside the Yellow Door, step up to the narrow wooden door at the end and then turn around right away. An area opened at the opposite end of the hall, releasing ghostly Undead Warriors. With them out of the way, they won't sneak up on you later. Inside the narrow wooden door is a smallish room filled with icky water, with stairs going down on either side, an overlooking platform at the other end, and inset sections in the walls on either side. The inset sections (with the red tapestries) are both doors: the one on your right goes outside, along a ledge up on the wall to your left, to the big overlooking area (the one where the Golems were) where you'll find the Green Door.

Before continuing, there's a bonus available. In the icky-water room, enter the red-tapestry door that was on your left. In here is a narrow compartment with a switch at the back. Hit the switch, and the walls on either side lower, opening up a larger room. After fighting the ghostly Golems, get a good weapon ready, and step into the opened room. The back wall opens, revealing another area with a crowd of Disciples of D'Sparil. There's a Map Scroll, and another switch on a column: it momentarily lowers the overlooking platform back in the icky-water room, where there's a Hellstaff. When you step onto the platform, the back wall above lowers. Step into the opened area, and jump back down to the stairs: two compartments on either side opened, each with an Iron Lich. There'll be additional items available here.

T-shaped hall
Go outside to the Green Door. Step up against it, but don't open it yet: areas on either side of you just opened, with ghostly Golems inside. After taking care of them, go inside. In here is a big T-shaped hall, with a stone door off to your far left, another stone door ahead, an overlooking area made of dark metal off to the right, and ledges across the hall on either side of the route to the center stone door. At the end of either ledge, look for and activate the section with the patterned texture. Both ledges will momentarily lower, allowing you to reach them. Find and hit the switch up on one ledge: this raises stairs to the dark-metal overlook. Go up there, look for a nook that opened when you stepped onto the overlook, and hit the switch inside. This opens the left-side stone door. An area just below the overlook opened as well, with a minor ambush.

There's a bonus available: go to the ledge opposite the one with the switch, and look for the patterned texture on the back wall like the ones that activated the ledges. This is a hidden door leading to a meandering route with a Phoenix Rod at the end.

Go to the room inside the opened stone door, where you'll find the Blue Key on an out-reach pedestal. Hit the switch nearby to lower the pedestal. When you step onto it, areas on either side just outside the stone door will open, with enemies inside, and also a big area directly ahead opens, with ghostly Undead Warriors and their red weapons. It might be easiest to run right away out to the main hall and fight the whole lot of them from there, but if you do, watch for red projectiles obscured by the other enemies and your weapons-fire.

Next to the center stone door, a small side room opened when you stepped onto the Blue-Key pedestal. Get a good weapon ready, hit the switch in here, and the center stone door opens. Immediately turn around: two areas on either side of that narrow section of corridor that led here opened, with a horde of Disciples of D'Sparil. This fight isn't too difficult, because they're all past the narrow end of the corridor.

Six teleporters
Inside the center stone door is a big room with a platform in the center, surrounded by six teleporters on out-of-reach pedestals. After clearing out the enemies, step up onto the platform. The walls around most of the room will open, making the room much larger and releasing a lot of enemies, mostly Gargoyles. (A lot of them will usually get into the teleporters, so you'll have them wandering around in areas, mostly outside, you thought you cleared out. They may be congregating outside the Green Door momentarily, if you want to take care of them all in one place.) Step into any newly-opened section, and a nook at one end of the room will open. Hit the switch inside, and another nook and switch at the other end of the room will open. Hit that switch, and the six pedestals will lower, bringing the teleporters within reach from the center platform. Also, outside, along the outer wall opposite the entrance to the battlement, a side room opened, with a teleporter inside that goes to the Green-Door overlook. With this, you won't have to take the long way around to get back to the teleporters any time you're working outside.

The teleporters, in clockwise order beginning with the one that was the nearest one on your left when you first entered the room, go to the following areas:
 * First: the caged-in area up on the far wall in the big lava-covered room. There are Wings of Wrath here. The teleporter in here goes to the entrance to the lava-covered room
 * Second: the small overlooking area outside on the far side of the Green-Door overlook. The teleporter here goes to the Green-Door overlook
 * Third: the small overlooking area outside on the far side of the Yellow Door. The teleporter here goes to the Green-Door overlook
 * Fourth: the small overlooking area outside above the ledge to the Green-Door overlook. The teleporter here goes to the Green-Door overlook
 * Fifth: the top of the battlement
 * Sixth (save this one for last): the Blue-Door overlook where you began the level

Last room
When you're done, go to and enter the Blue Door. In here is a big, tall room with several fat columns, and overlooking areas reachable by stairways past the other three sides of the room. Get the initial enemies cleared out, then go up the center stairs. The back wall ahead will open, with an Iron Lich inside. Also, doors in the fat columns that are opposite the stairs will open, releasing more enemies that may cause problems while you're fighting the Iron Lich. Explore the four overlooking areas, where there are several good items, then find and hit the switch up on one of them. This opens compartments along all of the overlooks and gives you a nasty Disciple-of-D'Sparil ambush; they'll be infesting the whole area. Once you get them taken care of, look inside the opened compartments and you'll find a switch in one. Hit it, and the remaining fat column will open, with the level exit inside.