The Crystal Plain is a vast strech of land covered with snow so coarse that the light from the sun shines off it like a mirror. It can be very dangerous to travel through during daylight, because the light is so bright it can cause blindness.
The Crystal Plain is a vast landscape covered in ice, and snow so course and dry that it forms a perfect prism for the light which in turn allows it to reflect so much light that if you travel across it during the day you will be permanently blinded. The only safe way to travel is at night, because there is very little light.
Before the Books
Before the books, when Fengo led the wolves from the Always Cold, at the time of the Long Cold, they passed by, or maybe even through the Crystal Plain.
In Spirit Wolf, Faolan and his friends enter the Crystal Plain on the journey to the Distant Blue. They made dens under the snow to protect themselves from the blinding glare the Crystal Plains during daytime.
- It is not stated weather or not the moons light can affect you, although it is assumend that it has little to no reflection against the snow.