Geistenmund Hills

The Geistenmund Hills are home to ancient barrows where some long-forgotten people were purportedly laid to rest. Centuries ago, Necromancers exiled from Bretonnia settled in the region and used their magics to raise the dead from the barrows with powerful runes, wards, and stone arches. These protections have grown old, however, and occasionally, someone will destroy the runes to free the restless dead. To this day, odd ululations can be heard from the hills on the darkest of nights, and mists from the river shroud the area in constant fog.

In this foreboding landscape, rumors of hauntings are enough to deter most from entering the area, and even armies on the march generally give the area a wide berth. The vast number of barrows in the area make a complete purge of the Undead who reside there impossible.

Source
Warhammer: The General's Compendium (supplement)

pg. 50