This is an evil little side adventure to spring on your party when they are asleep!
The backstory that introduces it is compelling and coherent, telling of conflict between two monasteries and a climactic battle in which one enacted a kind of magical 'self-destruct' as a last gasp of defiance... only it didn't quite work as expected, with one monk (who really didn't want to die with his comrades) left sort-of alive and trapped. He of course is now trying to escape, but for that he needs to entrap the living and use their life-energies...
The complex in which the characters find themselves is well-described, and allows for combat and investigation skills to be used as they attempt to figure out what is going on and how they are going to get out of it. They are not the only beings trapped there, and the monastery has its own guardians (mostly mechanical) as well, so there is plenty to fight. Tactics as well as stat blocks are provided just where you need them to facilitate the flow of the adventure.
It's a particularly neat adventure because it doesn't matter where your characters are or what they think they are doing (well, apart from sleeping!) when you hit them with it. It might be particularly effective with a party that has not had much contact with an 'oriental' style region in your campaign world (if you even have such a thing) but could equally well work for a game that's set in an oriental-style world. After all, as it involves other-worldly dimensions, being a demi-plane, it doesn't matter if it's native to your campaign world or not!
An Appendix has a new monk archetype, the tortured spirit monk (they reckon everyone's ki energy is there for them to exploit, so unless your campaign is particularly evil, it will be an NPC archetype), as well as a new monk feat and a couple of templates. Mostly these are used to explain some of the creatures to be found in this adventure, but you may find uses for them elsewhere.
Overall, something nice to have to hand. Perhaps your characters are getting just a little complacent and sure of what they are doing... so give them a little surprise one night!