Any gentle soul who thinks dungeons are fun and friendly places to go adventuring in will suffer a rude awakening should they visit this particular room (which is Level 1 Room 30 of The Dungeon Under the Mountain, if you're using that, although it can equally well be located wherever you want it.)
Sneaky and devious, and well-laid out for the DM, this chamber is certainly dangerous for the well-intentioned and generally 'good' party who might want to help the tortured figure that they behold... while there may not be so much danger for the more callous or evil visitors, who knows what harm they shall do to their own souls - or who may be angered by their inaction?
There is a single but ingeneous trap (complete with a few suggestions as to how to make it even more deadly if you wish), and a new spell - flicker - which makes a permanent-duration spell blink on and off rather than remain constant.
From the technical point of view, the capabilities of a PDF are stretched with the by-now familiar capability to 'rule the dungeon' in being able to set both the entire challenge and individual components of it to high, medium or low threat levels depending on the party you intend to visit the place. The plan - presented as both a small one for the DM and a larger one for those who want to use miniatures during play (and in this one, you really want to know where the characters are standing!) - can also be customised. There's even a space for your own notes.
It's a fine example of how to lay out a single room-based encounter, with potential ramifications that could last for the rest of the adventure.Rating: [5 of 5 Stars!]