I ran this as my first adventure. As a newly minted DM, it was a significant challenge to operate in Roll20 with such large maps, but I dearly wanted a megadungeon of my own. And a glorious megadungeon it was! Me and my friends had a blast exploring this dungeon. It required a ton of up front prep work before I felt like I was ready, and I mixed in material from various sources like Skerple's Monster Menu-All, and Wyatt's Dungeon of the Mad Mage Companion Guides (on the DM's Guild) which were INVALUABLE. I learned a bunch in the process, so honestly I'm glad that Undermountain was such a fertile environment to try building my first monster encounters, factions, magic items, traps, and so on. It is not particularly well formatted so I annotated the massive maps in Roll20 and broke them into manageable segments. My players would walk from one to the next and I would "load" the next map region and drop them there. We got through the first 2 levels before scheduling ended the game. I wouldn't run it again, but it had some great elements and it sparked my love of megadungeons even more.

Each level of the dungeon is (for the most part) narratively discontiguous, and as such it doesn't really hold up as a straight-run adventure. That being said, there are a ton of great ideas, NPCs, magic items, and dungeon ecologies that can be borrowed from DotMM and transplanted in your own campaign.

This adventure is a fantastic source of maps, monsters, encounters, and more that you can put it into your campaign setting with only a few of changes. It’s fantastic for when you need a quick dungeon map to use for a one shot, or to use as many smaller dungeons (although each level is still quite sizable on its own) scattered around the campaign.