When the bugbears stumbled upon this little respite, hidden in the middle of the dungeon they were startled. Secure, spacious, a fresh water supply, room for their temples, access the bigasstrouts they love to dine upon, and best of all....no damn adventurers. Their leader, a sly bugbear named Duttan has turned his small band of followers into near fanatic worshipers of Chrarnonk, the metal god. The statue was here from previous inhabitants and Duttan convinced his people they had finally found their way with Chrarnonk providing this wonderful home for them.
One point of note, the cavern near the bottom, that the water plunges into is actually a large shaft that reaches upwards over one hundred feet and connects to multiple other levels of the dungeon. The bugbears have not realized this yet. After falling to the chamber below, the water seeps through concealed caverns and eventually makes its way back to level one and is the source of the river coming from the rocks.