Bob's last stand... The Marine, cooperating with Tfear, has been sent into the Bob's stronghold to flood the place with lava. This must be done by hitting 30, count 'em, 30 switches scattered around the level (plus the final one down below). This level can take a very long time to do if you miss a few switches, and there are many strategies for beating it. I'm going to do it the fast way: Hit the secret debug switch inside a rock near the first terminal, make a single pass through the main complex, then head downstairs.
The terminal indicates that this is apparently one of several of Blake's bases, the other is named Hagakure and is probably the facility we saw on Slimy Things. We remember from Marathon 2 that Thoth was apparently in communication with the Bobs (or at least watching them); he was able to send us to Where the Twist Flops to assist them and possibly worked with them to capture the Hfarl. This will be important later.
This level also makes the second appearance of the Vacuum Bobs in the game, but they are a lot different now. They still hate you, but their hard death causes damage (it didn't before), they drop fusion ammo if killed carefully (they didn't before), the green ones are significantly stronger than the brown ones, and their bullet impact effect is the same as a ricochet off a wall. Is this a bug? They also hate the Potato Anuses that wander the level. Also flitting around are Kamikaze Ticks, who tend to explode if shot and do significant damage. This is also the first level to make major use of the "thunderstorm" trick, which first appeared briefly on Slimy Things: Synchronizing the flashing lights and ambient explosion sounds (and wind) to pretend that there's a major storm going on.
The buildings on this level hold some fun stuff, like a terminal (copy of the first one), pattern buffer, ammo, chargers, and some of the switches to hit. Most important, however, is the small "home base" provided at the top of the actual volcano, with buffer, charger, and terminal. Tfear tells us to seal the tunnels, and promises to teleport us out. I believe that this terminal was actually placed incorrectly, and should have been at the beginning of the level; it tells us to deactivate all the switches after we have already done so (also, it has a UESC logo, and the other has a S'pht logo). Switching the terminals would also have made the plot a good bit clearer, but more on that later.
Head down into the tunnels and get ready for some cat and mouse. Your Bob detector (see Naw Man He's Close) is useful again. Once you trigger the lava, you have three places you can go. First, you could head up the main shaft, which is the standard way. If you do that, you will be lectured on slavery and conditioning by Tfear, and promised a trip to a place called Grn'dl Prime, but teleported to Son of Grendel instead. Secondly, there is a secret here that I have no idea how to get: If you hit the switch and head off to the left of the elevator, you will find a room filled with Assimilated Bobs, and a door that will open, long after you're dead, to reveal an elevator up to a room full of Super Shield powerups. Finally, there's an elevated path back a ways where soem Bobs were shooting at you. Ride the lava up to it, run up ahead of it, and you'll be given a LOT of ammo and a chance to go all the way back through the overhead path to the "home base" at the top of the volcano.
Here, the terminal now has a message from Thoth. It is reasonable to assume that in this timeline, Thoth has been activated by the Bobs before the Pfhor moved in. As in Marathon 2, he has been watching the Marine's progress, and sees a chance to step in and help. Son of Grendel is obviously an important place to Thoth, as we eventually see on Strange Aeons. Perhaps Thoth knows that we have Durandal with us, and wants to talk to him. On to Son of Grendel...
