Hiding in the Dark... HELP!

I've used the "shimmering Elf stone," fought my way to the "deepest chamber." I get the message that I've found the "deepest chamber," but there doesn't seem to be anything to actually DO there. I leave, fight my way out only to find they quest hasn't updated and I still have to find the "deepest chamber!" I'm sure I'm missing something obvious, any suggestions?

Thanks!