Undermountain

Earlier this week, a FB post asked what was the best D&D supplement people ever bought. I answered with "Undermountain." Another poster asked me why. I gave a short answer,
"It was a mammoth resource. I have probably played or run 20 campaigns inside of it." I promised to expand on that explanation.

My initial statement is true. Undermountain is mammoth. 4 poster sized maps in the first boxed set. I love those poster maps. They immediately invoke a feeling of infinite space to explore. The terrain varies: water, worked passages, caverns, pyramids and ziggarauts can all be found on those maps. Even the city-within-a-dungeon Skullport is there.

Next, I want to take a second to talk about the Monstrous Compendiums. I loved those things. TSR executed them wrong, but they were still amazing. Why didn't they charge an extra $1-2 and print them on heavier paper? With only 1 monster to a page? That's why they excelled. They could be moved around and put into binders with your maps and notes. Undermountain came with 8 pages of those glorious Monstrous Compendium pages. The Elder Orb Beholder has even become iconic of the larger D&D universe. The other monsters within are strange, unique and evocative of the dungeon. Seeing those monsters all those years ago showed me how monsters could be more than cannon-fodder. They could be part of the lore of the dungeon itself (cough Xanathar cough.)

The books in the boxed set are the least inspiring for me. Campaign Guide does a good enough job of explaining how to run a megadungeon, but they are less evocative than other works in D&D. About 200 set encounters and six or so adventures seemed less than what should have been with those giant maps. But, the point was to give DMs the power to make Undermountain their own. It was just too much open space. Even notes like "Orcs control NE corner of level 1" or "this space is great for a hidden treasure and opponent" would have given new DMs a direction.

What I love the most about Undermountain is the Cards that came with the box. Eight of them: Pit Traps (1-3),Treasure Tables, Smash Traps, Snares and Lures, Dungeon Dressing, and Magical Doors all have their own reference cards. These short descriptions were more memorable to me as a fledgling DM than all of the splash and flair of the maps.
"Creatures passing through this door are instantly gated to a specific or random location . . ." How can a sentence like that not get you thinking about possibilities to put the players in.
I have never been very good at designing traps. Maybe these cards are why. A full five of eight are dedicated to traps, with the "doors" card having 1/3 of a side of traps as well. That's a lot of traps. And, unlike Grimtooth, these traps were (almost) fair.

I owe a lot of my D&D career to finding and loving Undermountain. Without it I would have never found other great dungeons. I would have never picked up Rappan Athuk, Castle Zagyg or Barrowmaze or the Grande Temple of Jing. Hell, I may have given up on D&D a long time ago if Undermountain didn't exist.