This level is... strange. It's completely flooded with green slime, it has architecture with no clear purpose, it has strange caverns and stairs and two towers at the far end. The plot indicates that it's some sort of important S'pht machine, a transmitter that will recall the eleventh clan in times of need.
The start of the level presents you with a neat home base: A pattern buffer, a 2x recharger, and several terminals, all with the same mysterious message: Your humans are safe but what are you?
The Enforcers on this level hate the Flick'ta nearly as much as you, so bezerk them at every opportunity. Beware of teleporting cyborgs when going around the main square area. At the north end, head into the deepest (extending furthest south) corner and look for one of the oddest secrets in the game, a huge room full of floating ammo. I'm not going to actually take this stuff, because it throws off the balance horribly, you can usually get a full load for every weapon by the time you get out.
In the northwest corner is your first objective: A platform leads up to an underground tunnel system filled with monsters. There are several platoons that teleport in in different areas, so be careful not to trigger them while fighting. In here is a switch that opens another door on the level. At the south side of the level is a strange cave with nothing but a spiral staircase and a ton of Flick'ta (and Enforcers).
The southwest corner holds the key to the end of the level. In here, past some tough monsters, are a pair of towers with switches at the top. Push both of these and report back to any terminal for beamout. Be careful when climbing around the south tower; it's possible to jump out of the second-floor window and into the courtyard below, dropping you into one of the very few suicide traps in the game.
There's another secret on this level, but one that doesn't appear in the game (any more). In one Marathon 2 screenshot, taken on this level, a Cyborg is observed to be bleeding red blood. This ties into a possible explanation for the Cyborgs discussed in the Scrapbook: They would be captured Bobs attached to machines, a crude Pfhor imitation of mechanically-enhanced human soldiers such as yourself.
