The walk to the spot where the dragon hid itself was not easy. Chris might have found the entrance but the true lair was hidden deep inside and it wasn't easy to reach the spot.
It has been three centuries since the old dragon hid itself deep inside the mountains. When it hid, it collapsed the pathway leaving only a small pathway for air. Three centuries in, a lot changed.
There have been many landslides that happened in these past three centuries, either naturally or due to devastations caused by powerful monster fights. Whatever it was, it made it difficult for Chris to traverse through the path to the hidden lair.
Sometimes he had to crawl, and sometimes he had to slide down the path. It wasn't a straight line. It was filled with dangers too.
Though the path was closed to the outside world, there are a lot of monsters that exist in the underground.