great interactivity. In particular, the troglodyte spy in 30, skeletons in 11, prismatic spy in 43, provide lots of opportunity for the dungeon to avoid being static, and can be used for counterplay for party or dungeon inhabitants.
Flavor/theme seems somewhat random. Clearly fantasy, but not very tightly focused. may appeal to others, but doesn’t grab me.
Of course, definite NG layout style & great art by Treme.
Level design is in line with OSR ethos. There is easy passage to level 2 (e.g. 1 → 2 → 3 → 20 → 37) and thus allows lots of choices of encounters to take on, rather than being stuck on the mooks on level 1.
several hard things to fight (ooze priestess, prismist, dragon) which again, offer options for all levels.
Overall I find this dungeon slightly more interesting than average. Nothing bending the brain, but includes all the usuals of the OSR in dungeon design. You are very likely to have a fun time. I think I would have trouble keeping track of the moving parts (e.g. spies), but mostly because I haven’t done that terribly much in my games.
I’ve run/played Incandescent Grottoes with friends and family, and it does offer a lot of charming details.
The dungeon layout is nice and varied - it shifts between caves and worked rooms, which I always enjoy. A lot of the traps are fairly sensible and allow players to mess with them if they catch them in time.
The enemies are a bit random - The Troglodytes made kind of no real sense in this dungeon, and the Necromancer is listed as an entire “faction” in and of themselves, but only appear on the random events table so we never met them once in our entire playthrough.
The weird ooze temple is great, I love me an ooze cult. That part of the dungeon is fairly coherent in theming and enemies.
I quite like the little through-line of the Prismist and the whole “omg the emperor is an illusion!” conspiracy theory stuff, and our group ended up doing a lot with that, up to and including ambushing and killing the imperial agents sent to look for her and helping her out of the dungeon.
One big positive is that there’s an actual dragon in the dungeon. More people need to put dragons in their dungeons, it’s in the name of the game people! Come on!
Overall I think Incandescent Grottoes is a very solid dungeon, though nothing particularly standout in terms of design. It very much feels like, well, a B/X dungeon. The enemies are mostly just things you find in the book with maybe 1-2 interesting choices, and that is fine because I don’t think it tries to be anything else.