EDIT: SOLVED

I probably played this dungeon crawler game around 1997-2001-ish but I could be wrong on the dates. My friend gave me a CD with a ton of games on it, so I don't super remember the box art.

I think the name might have had the words "pass" or "vanguard" or something like that in the title (but that could easily be a red herring and misremembering.

The game was very grim-dark, not least because the draw distance was poor. Unlike most dungeon crawlers, I feel like this one had 360 degrees of turning (I feel pretty certain of this but I could be wrong on any of these points). I am gonna bullet point all the things I remember for convenience:

- I believe the intro video showed this fortification that connected two mountain passes.

-You start above ground in this little canyon. There was like a trader and I think you maybe already find someone to join you in the canyon but I remember this seeming like a random event.

-Game had 360 degree movement but my memory is hazy.

-I remember having to overheat a boiler at one point, maybe an hour or so in, to explode it.

-pretty classic dungeon crawler but I remember you could kite monsters.

-I don't think you really go back to any towns or anything, you are just in this underground for most of the game and then I think maybe you get to that fortification connecting the pass at one point.

-I'm pretty sure the point of the main quest was to either defend or take down some kind of magic forcefield the fortification was keeping up to protect the pass. One of the two.

-game had a magic system but I don't remember much of it.

I appreciate any help. I just worked through dungeoncrawlers.org's complete list and don't felt like I saw it there.