All of this rang a vague bell, especially the pools, but I couldn't quite put my finger on it. So I floated the question past a random group of R&D folk who happened to be nearby, and Mike Mearls was the first to chime up with B1, In Search of the Unknown
, from 1979. The area is the Caverns of Quasqueton, and "R" and "Z" are Rogahn the Fearless and Zelligar the Unknown. The chained ogre must have been added by the DM.
What do we win?