Marked by Dark Cultists Witchcraft in Diablo III are not mages, spell casters, witch crafts, they are servant of Baal who guard the temple of doom where Baal's hive of darkness and deceive. Diablo III is a game that you will enjoy knowing the creeps, actually all kind of dark evil units.
Witchcraft or Spell caster or dark mage? you decide what you call them but they are not the one you can trust with, they might be helpful but they will turn you back down.
