The really fun thing about the module is that, since it's a "teaching" adventure that lacks monsters, it spends a lot of time focusing on interesting details of the dungeon. For those out of the loop, the idea is that the PCs find a map to the subterranean lair of a pair of long vanished adventurers, the magic-user Zelligar and the fighter Roghan. There's a room overrrun by fungus, a chamber with lots of weird pools to mess with, and so on.
My favorite bits concern the secret chambers of Zelligar. They have lots of little bits that point to Zelligar as a less than nice guy. His lab has an empty coffin, the skeleton of a slain enemy, a tapestry made of human skin, and a few other baubles.
I really liked the idea of Zelligar poking at things best left alone, so there are a number of extraplanar critters in the dungeon and chambers with weird, demonic themed puzzles and oddities.
Today, I picked up this Dreamblade miniature on the free table at work. It looks cooler from the opposite side - it has a big, steamroller splattered with blood. I liked the idea of Zelligar leaving behind a really nasty guardian to kill intruders. So, with that in mind, here's what I did:
If the party takes a short rest in the dungeon, roll 1d20, +2 per prior short rest taken during this expedition. On a 15 - 19, the party faces a wandering encounter (I haven't placed monsters in the dungeon yet). On a 20+, the Doom Crusher appears 2d10 squares away from the PCs and moves to attack. It cannot open doors, and scrupulously avoids destroying the furnishings and decorations in the dungeon. Otherwise, under Zelligar's 30+ year old orders, it attempts to crush intruders as an encouragement for them to leave.
I'll work up stats for it soon, but I'm thinking of making it a level 10 elite in a dungeon aimed at level 4 characters. I'll also add in some signs of its presence, like a crushed chaos warrior or orc here or there, pulverized skeletons, shattered armor and weapons scattered in the halls.