The Serpent's Throat
After the point where the two tunnels rejoin, the tunnel widens. Clear to everyone, in particular to Dellrack's dwarven eyes, this area was much easier to dig. Unfortunately, the side-effect was that it was much more difficult to keep supported. Wooden supports were brought in to keep the walls and ceiling up, yet still, sand and water have been steadily seeping through the cracks.
Finally, a wide-flat wood-supported hall leads to a short flight of wooden stairs up to a solid-looking door, flanked by sputtering torches. Strangely, the door has no latch, lock, or handle - instead there is a rusty steel lever on the wall beside it.