I don't understand one of the Special Rules in encounter 2 of Rellegar's Rest in the Heirs of Blood campaign book. Under "Special Rules/Finding the Light/Green" it states:

"The figure that revealed the token tests (perception). If it fails, it's controlling player removes that figure from the map and places it on the unique space."

What is the "unique space"?

Unique spaces are those marked with the "X". Usually these are red, some quests have unique spaces of other colors.