After hiking halfway up the side of an extinct volcano, you pause by what looks like a cave entrance. The light shines into the opening enough for you to see with ease, but you can see that the tunnel-like entrance veers off to the left after about fifteen yards. You decide to follow this path into the mountain, which curves a series of times before it branches off into two tunnels. White light shines out of the tunnel to the left. The right is completely void of any light whatsoever, and looks almost as dark as a black hole.