The Warrens

In the southern foothills of the Black Mountains lies a region of unusual rock formations known as the Warrens. The rocks for a virtual labyrinth of natural corridors, walls, and chambers, which are perfect hiding places for ambushers and cutthroats. A famous group of mercenaries called the Carrion Band is rumoured to make its home here.

Souce
pg. 56
 * Warhammer: The General's Compendium (supplement)