On kingdom of loathing how do you get to the boss bat

When you are a level four, go to the Council of Loathing to get your quest. Then you'll get a new location on your map in the Nearby Plains - "the bat hole", fight there till you get something that's adds to stench resistance or combine two bum cheeks to make an asshat. Equip it and adventure in the middle area until you get three sonar biscuits. Use them outside of battle to break the rocks and the very bottom area in the bat hole will be the bat boss' lair.