A Winding Series of Tunnels                            -      N      - 
(-------------------------------------------------)     - <---(M)---> -
                                                        -      S      -

You are walking through one of the many tunnels that lead deeper into
Hellbent Mountain.  They twist and turn seemingly at random, and it is
rather hard to get your bearings.  The walls here are rough and rocky, and
look like they formed over a long period of time.  Clearly, this section of
the cave was created by erosion, not volcanic activity as you had earlier
thought.