There's the "Mr. Freeze" archetype. In this scenario, the wizard isn't looking to raise undead generally. She is looking to return one specific person back to life. A lover or child, usually. To do this however, to return someone to true life, she needs to study and understand death. Such a wizard would focus less on undeath, and more how death itself works, and how the underworld and life after death is handled.
See Orpheus and other similar myths. (http://en.wikipedia.org/wiki/Descent_to_the_underworld)
See Orpheus and other similar myths. (http://en.wikipedia.org/wiki/Descent_to_the_underworld)