Long before we had a movie about Spelunking, we had The Descent for Quake. Of course the interesting thing is that Descent, a game from the 1990s, was one of the first popular games to have full 3d. It seems ironic that The Descent would end up as a level in Quake.
We get our first broken level! When I mean that, I refer to the fact that it is entirely possible for the level to crash on you at some point during a normal play session. In this case, that would be in the starting room. Though I cannot seem to prove it due to its random nature, I am wondering if it has something to do with the Ogres grenades colliding with the Door (it has something to do with that Door). For some reason, if I can kill the Ogres quick enough I can usually avoid a crash.
Beyond the thought that this level is broken and therefore frustrating, it is improved in general design to E2M1. For some reason, this level reminds me heavily of E1M3 and may have even been made by the same level designer (it is stuff like this that makes me miss the credits that appear at the start of each level in Unreal). Maybe it is due to the metal platforms suspended over Lava or the need to kill things to progress. In any event, this level basically is Button central. The first three rooms are basically Button puzzles.
Oddly, there is a Rocket Launcher available in this map on Normal difficulty. I wonder if this was a mistake and intended only for Deathmatch, or if it was actually intended to be on one difficulty. Also, Hard/Nightmare is a bit easier at the end personally due to the large number of Rockets in the map combined with an enemy weaker to Rockets (the Vore) compared to one resistant to them (the Shambler).
If you all were expecting me to keep up the whole "not use anything not found in this Episode", I kinda failed here. While gunning down the two Shamblers by the Gold Key, I ran out of Nail ammo (I did use the standard Nailgun when I could have used the better Super Nailgun). Quake automatically switches to the best weapon if you run out of ammo, so I immediately started firing the Thunderbolt and used 2 charges before I realized what was happening. Still, a single Double-Barrelled Shotgun blast would have been enough to kill that Shambler.