The forest was dark all throughout the year with the only source of light being a purple star mist that enveloped the forest. The forest was a literal version of an oxymoron which was why it was always called the nightmare paradise.
The forest was rich in resources and spiritual qi, and the purple mist helped to improve one's comprehension abilities. However, the forest was also home to spirit beasts and spiritual plants that had taken advantage of those conditions to develop themselves. There were also natural phenomena, dangerous at that, that continuously flooded the place such as lightning storms, and because of how rich the area was, tribulation lightnings were not in short supply either.