Dungeon23 Room 239 (The DeepWilds Tradeway)

PCs will feel rather than see the cavern open up on one side into a deep crevasse.  On the left side next to the wall are 23 Svirfneblin Deep Gnomes (AC 2 and better HD 3+6 FF pg. 84) with a Giant Pack Lizard (AC 5 HD 3+1 MM pg. 61)

Additionally every 6 turns (60 minutes) there is a 30% chance that a swarm of bats (1-16) or giant bats (17-20) flying up out of the crevasse. Be glad its just bats, there are much worse things down here... in the dark...