Ashala enters the tunnel, the ceiling not far over her head and the walls irregular and rather tight. Certainly, travel would have to be single file. The tunnel barely goes five feet before it jags to the left, and again not so far before jutting the other direction. Nathros' underground intuition tells him that the path is more or less headed in the same northerly direction and sloped down somewhat, though probably imperceptibly to his human companions.
The tunnel opens up into a roughly circular cavern about twenty feet around. While she doesn't spot it right away, once the torch bearer behind her enters to room, two dark figures can be seen twenty feet overhead on the ceiling. Giant bats. They turn their bat heads in the direction of the newcomers.
SpoilerPCs win initiative.