This is a strange level... Somewhere deep underground, the last of the Bobs are fighting off a Pfhor invasion. And Thoth dumps you in the middle with vague instructions about returning to your people.
This is a very simple level: Just run around and kill everything. The architecture is mysterious, but it doesn't really seem to be anything. There aren't any puzzles, or anything to find. Just kill every monster available and head back to Thoth for more "instructions".
There are a few interesting places. The "Abandoned Homeworld for sale" terminal under the lava in one area, with a super shield powerup. The vast amounts of ammo in the southeast area. Thoth's final message. All in all, this level seemed like filler to me.