Shamans

Shamans are the key religious figures of the monstrous (such as Greenskin or Ogre), or less civilised Human tribes. It is their job to act as intermediaries between the mortal realm and the spirit realm. They must drive off evil spirits, while placating benevolent ones. They have a special relationship with their tribe’s tutelary spirits. Frequently ancestors, these spirits watch over the tribe and protect it, as long as the shamans show proper respect and make frequent sacrifices.

Apprentice Shamans
The touch of magic is rarely a welcome one amongst the monstrous tribes. Those with magical aptitude are often driven mad by unsettling dreams and their strange behaviour can lead to their deaths at the hands of superstitious tribesman. A few learn to cast minor spells in a manner akin to the hedge wizards of the Empire. The best of these candidates are taken as apprentices by tribal shamans. While this does safeguard them against murder, they become virtual slaves of their shamans and must endure years of pain and humiliation before finishing their apprenticeships. If they survive the experience, they have taken the first step on a path to power among their tribe.

Shaman Lord
The most powerful shamans are the shaman lords. They have mastered spirit magic and kept their tribes strong. Tribal chiefs look to them for advice on nearly everything and they treated with something approaching awe. In some tribes, shaman lords become chiefs themselves. A few become powerful enough that they dominate several tribes and have many lesser shamans in their service. Like all powerful figures in the monstrous tribes, however, shaman lords must keep an eye on ambitious subordinates and make examples of those who dare to challenge them. b

Source

 * Warhammer Fantasy RPG 2nd ED -- Old World Bestiary pg. 80 81