Be sure to save your game before leaving Egos, as it's a long, long time until you'll see a pattern buffer again. In fact, this is the only thing that makes Cauldron difficult - you won't be able to gain access to a PB until you've basically eliminated any threat of danger. Matt, you might want to consider redistributing some monsters to later in the level to give it more balance. Although the level is otherwise pretty straight-forward, it contains what is absolutely the coolest elevator I have seen in any Marathon scenario, and that's saying a lot. More on that in a moment.
You have teleported into Mece's lab and your mission is to shut down the cryo units so as to distract Mece while the Kinetic's captured crew members get away. Still no explanation as to why you can now teleport - are you listening, Matt? You start out in the first of two square rooms that comprise an armory with lots of shrapnel and magnum ammo. Upon exiting, turn left and head back into the far left (southeast) corner, where you'll find a 1x recharger - your lifeline until you get upstairs. Immediately there will be a couple of troopers coming after you, and some troopers from above will likely drop down as well. Circle clockwise and they're pretty easy to take out. A bit more difficult as you work your way into the maze of the complex are two invisible major compilers. The difficulty is that there are a bunch of compilers on the second level looking down on you and, hence, just as you think you have things under control, you'll be getting zapped from an unexpected direction. You can always easily retreat under the upper hallways, out of reach. There is one terminal on the lower level - it contains a message from Mece, who is not particularly happy with you. This is also the exit terminal.
Matt, there is a serious bug here. As you move about the large lower level, you'll see two large green specimen containers - one in the right-hand (northeast) corner and one on the left (northwest). You can shoot the one in the right-hand corner and will find a human form inside. *Gasp* If you shoot or otherwise break the left-hand one, however, the game will crash. Hard. Every time. Good thing the Classic Environment loads quickly under OS X. Hopefully this will be fixed in the next release. To gain access to the upper level, you need to shoot a switch in the northernmost section of the upper level, that is visible from below. You need to shoot the south facing switch - the north-facing switch opens access to the PB, but we can reach it directly once we're up there, so why waste the ammo now?
A door in the southwest area of the map will now be open, granting access to a large specimen storage area that is filled with invisible compilers and wasps. The wasps will come out and play, but you'll have to go in after the compilers. Inside this room is a central elevator - absolutely the cleverest design I've seen. It’s sort of like a glass-enclosed elevator you would find in a fancy hotel. Flip the switch and you will see it descend. Walk around to the opposite side and a door will open once the elevator has descended. Step inside and elevator takes you to the second floor. This is so cool, and it’s all because of the wonders of 5D space. Behind the elevator door is an ordinary platform, but it's not visible from outside the elevator. Instead we see an overlapping space that contains a descending platform from above. The illusion works, and it almost makes you think you're using a real elevator.
Once upstairs, wind your way along the corridors you previously saw from below. You'll eventually come to all the compilers that were shooting at you before - take 'em out if you haven't already. Now go back to the north-facing switch and open access to the nearby security alcove, where you can finally save your game, now that almost all the fighting's over. A switch in this alcove opens access to an alcove with another switch you need to flip, as well as to a shortcut back to the first floor. You'll shortly come to another 1X shield recharger and a circular room with some compilers, one of them invisible, and a couple of terminals - one a pep talk, I think from Shaki, and one with instructions on shutting down the cryo units. Head down a nearby stairway and into an alcove with a switch. Flip the switch and return upstairs to find that one side of the circular room has completely opened up, revealing another specimen storage area as well as the four switches that need to be flipped to shut everything down. Flip them and then return to the terminal on the lower level to be transported to Mece's Inferno.