The light was a rare commodity in the underground space. The only way to see something was to generate light yourself. Of course, as cultivators with Spiritual Energy, it wasn't anything hard to do. However, it didn't make things much better. The Decaying Fog around made the light stop at just three or four meters away from the origin. In some places where it was more concentrated, it wouldn't even matter that much.
What cultivators relied the most upon going underground ended up being their Spiritual Sense. It could travel much further, not to mention that it was an all-encompassing sensory ability. Still, as mentioned before, Spiritual Sense was also affected by the Decaying Fog. Even those at the Peak of the Core Formation Realm couldn't see much more than 100 meters around or so.
