Under Shattered Mountain is an OSRIC module designed for 58 adventures of levels 912.
Shattered Mountain... an evil landmark looming over the countryside. In ages past, the mountain roared as a volcano and rendered the surrounding area uninhabitable, and then suddenly went quiet. Centuries later, investigation by adventurers revealed the volcanos core to be mysteriously sealed off, although large tunnels appeared to meander through the ground underneath. In time, various creatures made those tunnels their homes, though few dared to strike out into the populated areas due to the champions which defended civilization.
If you enjoy this adventure, look for future releases in the Advanced Adventures line from Expeditious Retreat Press.