As you get to the point that your torch illuminates the cavern on the right, you see that the walls curve up nearly 10 feet in height, to a ceiling covered in cracks. There is a thin veneer of dark liquid on parts of the walls and in places on the ceiling, but it isn't dripping. Turning to go back the other direction, you get to the door leading to the left. The dripping intensifies there, and you see the well-worked cut stone walls (not naturally worn, like the right hand cavern, these are intentional walls) are coated with that same slick dark liquid.
I will pause you right there. After the concert, we'll play out your continued exploration of the chamber OR your group's decision to take a long rest in the current cavern space you've uncovered. Please decide as a group and let me know how you all want to proceed: Long rest in the first chamber, long rest in the upper right dead end chamber, enter and explore more to the left without resting.