I remember reading in some 2e source of a potential encounter between PC's and a fully matured Ancient Baatorian somewhere in the depths of Malbolge or Maladomini. I remember it looking like part of the tunnel, or something to that extent.
There is a problem. Namely, I don't remember it exactly and I would like to for the project I'm currently working on. Thing is, I don't remember where I read said snippet. If anybody has a better memory than I, would they please point me to the source I'm thinking of?
Hellbound: The Blood War.
The War Games booklet.