"Nah, it's not sewage, but it's designed to look like it is," Escobert says with a laugh like tumbling boulders, "Used to help escape in case of a siege. Never thought I'd see it used, though!"
The old dwarf leads you down to the ground level and to a rarely used section of the keep, to a iron-bound door. He takes a ring off of his belt and unlocks the door, revealing a long, dark tunnel. It's only about 5 feet wide, so you're going to have to move single file. He hands Bughu an old iron key, "This is the key to open the grate at the other side of the tunnel. It's all in your hands now... be careful."