(normal hunting or overland movement)
Your group falls into a small chasm that opened beneath your feet. (Climb out immediately or continue) if you continue the climb out collapses, onward or die.
Where are we?
Find your way out. Survive.
5-10 rooms
Some climbing?
Some swimming?
A few (random odd creatures not found in your hunting area) A reclusive dangerous hermit? Trolls? Undead?
A way out?
Good chance of decent treasure.
Can happen randomly anywhere and collapses in on itself afterwards. Level +5-10 to make it a serious challenge.
John