Yulya sees something odd about the Eastern wall. She approaches and tries to touch the wall, the illusion protecting the area suddenly becomes clear and a passage leading down is shown.
There is a ladder leading down, it seems to be made for smaller humanoids to access, but it's large enough for passage by humans. Remnants of a hoist remain where heavy loads and a space just large enough for a minecart could be lifted up and down the shaft and placed on a rail, again the rails have all been removed in this room long ago. Yulya is certain there are no traps, the ladder seems to go down about 40ft to another room, barely lit by some unseen source which could be a torch or glowstone.

Ashley walks casually forward as she looks for more ore samples along the walls and ceiling.
"Yulya, if I spot something, will you fly up and get it?"

The rumbling sound intensifies until it seems like there could be as many as 4 additional sources, then stops, a crunching sound echoes throughout the chamber then all is quite.
"Don't even think about going back up there, and count ourselves lucky if they don't follow. I'll tell them personally, assuming we ever see them again, that they need an exterminator."

Yulya I am keeping the ring for now so I an scout! I'll return it as soon as we're done exploring. So stay behind a bit with your tingling armor!

Yulya casts Bane on the Bulette.
It saves against the spell.