Hub 4: Desolate Garden

Desolate Garden is a secret level in the fourth hub of Hexen. It is only accessible by crossing a linedef in the map Bright Crucible in the first hub and pressing a switch in the map Sacred Grove in the second hub, or by using the "casper" cheat code.

It is the 25th map in Hexen, but is named MAP26 in the WAD file.

Walkthrough
In this map, you can collect all three pieces of your fourth weapon, if you haven't done so otherwise.

Look for the three superweapon pieces here:
 * Behind the exit portal, where you overlook the main courtyard
 * In the eastern slime trap room.
 * After triggering and disarming the slime trap (by pressing the eastern-most switch), return to see the final piece of the weapon.

You will start in an open square. You’ll be greeted by Dark Bishops firing on you from a window in the eastern wall across from you. There are Green Chaos Serpents in the window on the western wall just behind you, and they will start firing when they notice you. Around the central square, there are 8 outer switches and 1 center switch. The outer switches will randomly rise and fall, one at a time. As you pull the switches, the level will open up. The order you activate them doesn’t matter, rather, the level will change after certain numbers of switches are pulled. The exception is that the center switch will always be the last to rise.

Each time you pull an outer switch, a random monster will appear. It could be any of the following - Ettin, Afrit, Green Chaos Serpent, Centaur, or Slaughtaur. The center switch teleports in several Dark Bishops.

If you haven’t already, you should pull all nine switches to open the way to the exit portal. You can also check the western corridors for the Krater of Might. Having completed the level, you can take the portal when you’re ready, which will return you to where you left from Forsaken Outpost.

Mage Class
In addition, for every player class on every skill level there are 8 random monsters which are spawned when outer switches are pulled. They can be of the following kinds: Ettin, Afrit, Green Chaos Serpent, Centaur and Slaughtaur.