Played this on Total Carnage and managed to finish it (obviously I used the pattern buffers). I didn't manage to get all kills and played a little roguishly, but still...

This will stay in my mind as one of the best and most memorable Marathon levels I've ever played. It really feels like a modern Doom challenge map, being a gauntlet of high-concept combat setups. And what setups! Each one is overflowing with creativity and many utilize elements and mechanics that only exist in Marathon and in no other game, including some crazy ones involving your movement. It's a challenge fit for a Vidmaster, yet at the same time it always feels fair once you realize how the encounter's flow should actually go -- just as it should. More than that, the water/Pfhor theme has a very striking atmosphere, compounded by the niche bullet-hell game music. The map has no terminals, so you're either in it for the combat or not at all. The closest thing I could possibly compare this to are the maps for other classic shooters made by Tango, such as his set for Doom Godless Night. It oozes the same sort of colorful experimentation with in-depth battle setups. More than just being an exercise in pure enemy placement, the weapon choice is exquisitely unusual, with the TOZT getting in this map alone probably more limelight than in any one of our dozens/hundreds of regular Marathon playthroughs. Here's hoping the future, no matter how far-flung, sees more of this school of mapping for Marathon.

PROTIP for aspiring players: If you have a lot of difficulty understanding how a given fight should go in Total Carnage, try saving before it, playing the encounter on Normal mode to study its flow/win condition, then going at it again with the legit mode. If it seems still impossible on Normal, you are probably missing something. You might find something out through exploration.