In the Warrhammer World undead wizards are known as necromancers rather than liches; a necromancer who fails, for whatever reason, to control the process of becoming undead becomes a ghostly wraith.  A liche is simply a supremely powerful necromancer. The most famous are Nagash, the powerful "Father of All Undead", and Heinrich "the Lichemaster" Kemmler, the most feared necromancer in the Old World.