The White Dwarf wears a disguise until he is ready to reveal his true self. This disguise is usually in the form of a huge cloak he wraps around himself to conceal his enormous white beard, a clear sign of an Ancestor!
The White Dwarf has thespecial rule. However, if the unit he is Hidden in is wiped out or flees then the White Dwarf will be revealed, and will stand his ground even though the rest of the unit may be fleeing or slain. Place the model in the middle of the front rank of the unit, then move/remove the rest of the unit as normal. The White Dwarf will then operative as a lone character as normal. The White Dwarf may never be the army's , but units he joins may still use his Leadership once he is no longer Hidden.