The Blight

The Blight is a large moor within the Western Oblast that is mostly uninhabited. A few tirsas dot the edge, making their living by mining peat, but the central regions have no known Human residents. They are known to be home to monsters of various kinds, including Greenskins and Beastmen, as well as Mutants. Parts of the great Chaos Horde are thought to have taken up residence here; certainly, raids by monsters have increased in recent times. The swamp is generally thought to be tainted and to have an unnatural origin. Many tales report there are great treasures hidden in the centre, but most people think that these are just tales.

Source
pg. 58
 * Warhammer Fantasy RPG 2nd ED -- Realm of the Ice Queen