I love this game series and I actually got this supplement after the newer caverns of chaos. I had taken my party through there and done the scouting mission and decided maybe that was too hard. I thought this earlier work would be easier. Let me tell you was I wrong. XD
My party which I have been through so much with has as of a few moments ago met their end inside the gooey center of an acidic cube. It devoured them one by one as I helplessly watched. No one survived. The supplement certainly lives up to the name fiendish foes.