The floor of the hallway seems well-trod and the breadth of the passage sufficiently wide for easy passage. It travels a goodly way with a subtle downward slope, though Nathros notices as it begins to slope upwards again in the last several feet.
At the edge of his light, Nathros spots what Creeper described - a kobold, a bit better dressed and slightly larger than the others, digging foolishly at the bottom of a cave-in that covers the entire tunnel ahead. He clearly doesn't hear the approach, but notices the light increase behind him.
* post roll count doesn't match database